Java Full Course in 10 Hours | Java Tutorial for Beginners [2023] | Java Online Training | Edureka

Aug 15, 2023

Java Full Course in 10 Hours | Java Tutorial for Beginners [2023] | Java Online Training | Edureka

🔥Edureka Java Training (Use Code ”𝐘𝐎𝐔𝐓𝐔𝐁𝐄𝟐𝟎”): https://www.edureka.co/java-j2ee-trai…
This Edureka Java Full Course will help you in understanding the various fundamentals of Java programming in detail with examples.

Check out Java Tutorial Playlist: https://goo.gl/ES3dI3

This Java tutorial for beginners covers the following topics:
00:00 Agenda
3:36 - Introduction to Java
23:46 - Java Environmental SetUp
28:43 - Java Internals
35:05 - Java Working
38:21 - First Java Program
53:27 - Modifiers in Java
54:34 - Access Control Modifiers
1:00:12 - Non Access Modifiers
1:10:05 - Variables in Java
1:14:59 - Data types in Java
1:25:52 - Operators
1:28:56 - Operators Types and Examples
1:33:11 - Control Statements in Java
1:35:51 - Selection Statements
1:37:17 - Iteration Statements
1:44:04 - Jump Statements
1:46:06 - Methods in Java
2:09:00 - Arrays in Java
2:27:50 - Strings
2:52:45: Classes and Objects
2:57:17 - Java Naming Conventions
2:57:30 - Types of variables
3:01:30 - Constructor
3:19:09 - Java Static Keyword
3:24:32 - Java this keyword
3:29:27 - Object-Oriented Programming Concepts
4:29:44 - Interface
4:50:55 - What is a Package?
4:58:12 - Access Modifiers
5:05:00 - Demo - Access package from another package
5:08:55 - Regular Expression
5:21:50 - Exception
5:31:45 - Exception handling
5:50:27 - XML in Java
6:36:00 - Serialization in Java
6:54:00 - Wrapper Classes
6:58:06 - Generics in Java

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Content

0 ->

10.8 -> Java is one

11.6 -> of the most fundamental programming languages

14.35 -> that anybody can learn despite being so simple.

17.2 -> It is a Marvel

18.065 -> what can be achieved with the use of java?

20.7 -> Hi everyone.

21.5 -> I welcome you all to this Java full court session

24.388 -> by Edureka,

25.278 -> but before we begin, let's look at our agenda for today.

28.532 -> So we're going to start out by talking about Java, what it is,

31.905 -> and why do we need it?

33.2 -> Then we're going to discuss a few basic

35.4 -> concepts like variables

36.702 -> and data types in Java followed by which we are going to talk

40.1 -> about operators control statements and methods.

43 -> We are also going to discuss the meat and potatoes

45.9 -> of this session classes objects

48 -> and object oriented programming Concepts

50.5 -> in Java followed by which we are going to talk

53.3 -> about exception handling

54.9 -> then we're going to discuss Java collection Frameworks

58.369 -> and finally close this Action by discussing the Dom parser

62.1 -> in Java also do click

64.2 -> on the Subscribe button to never miss an update

66.905 -> on the hottest Technologies by the Edureka YouTube channel.

70.2 -> Okay, before we start off let me introduce myself.

73.082 -> I am vinoth and I have been

74.5 -> with this industry IT industry specifically

77.2 -> into Java development for last 12 years.

80.1 -> Alright, so the first topic is about introduction to Java.

85.5 -> So what are we going to cover in this particular topic?

88.8 -> So it's going to be introduction to Java

91.7 -> what Java is all about will have Java installation done as well.

96.5 -> So that you guys can use it in future.

98.767 -> You guys can try your hands on we'll talk about modifiers

102.165 -> and variables in Java.

103.5 -> This is pretty much similar to

105.264 -> what we have in other programming languages will talk

108.3 -> about Java data types as well,

110.3 -> which is nothing but data type

112.3 -> as we have the it's a storage for different data types,

116.407 -> right or the data

117.7 -> that is store whatever you want to process.

120.1 -> Song is first put into memory

122.1 -> and that is what data type is all about.

124.7 -> So you have different storage is

126.3 -> like for character you have something else

128.8 -> and for float you will have something else for long.

131.8 -> We will have something else

133.2 -> sort of data type conversion in Java.

136.6 -> So so you could convert from one data type

139.823 -> to other data type in Java.

141.9 -> There are implicit conversions done.

143.9 -> We're in the programmer need not take care about it.

146.9 -> Java programming by itself would take care about converting it

150.6 -> which is implicit conversion and there are few conversions,

154.9 -> which programmers have to take care about they

157.9 -> have to explicitly mention

159.7 -> that you have to convert from this data type

162 -> to this data type.

163.3 -> And if you don't do it

164.4 -> you would end up in compilation errors or something.

167.1 -> We'll talk about operators operators are nothing

169.7 -> but the operators

170.734 -> that work upon this data type

172.553 -> and which is nothing but transformation.

175 -> So you kind of use this operators to add up for say

178.9 -> for example Of two integers you want to add it up.

181.9 -> So you would have this operators used.

184.4 -> We'll talk about control statements in Java as

187.692 -> well control statements.

189.51 -> Like you have

190.494 -> if else and for loops and stuff like that,

193.7 -> so we'll talk about it.

195.035 -> So Java is pretty much similar

196.95 -> to other programming languages thing is

199.384 -> it has some unique features

201.076 -> which makes it really important

202.928 -> in the current industry the IT industry

205.3 -> when it comes to Big Data and stuff like that.

207.8 -> So we'll touch base on all this important features of java,

211.582 -> which would help you to understand.

213.8 -> Why do we really use it?

215.6 -> Alright.

216.1 -> So the first topic is Introduction.

218.8 -> So what is Java so Java as we said the programming language

223.5 -> which has object-oriented programming model.

226.2 -> So when I say object-oriented programming model everything

229.5 -> in Java is taken as an object.

232.3 -> So object is nothing

233.756 -> but something that has got State and behavior say for example,

238.198 -> you have chair, right?

239.722 -> Jed has got a particular State

241.8 -> and it has got a particular Behavior.

243.917 -> If you do something if you move it,

245.709 -> it would go this way

246.8 -> and that way and stuff like that.

248.6 -> So basically any object

250.369 -> if we think about in reality realm any object

253.8 -> for that matter would have some kind of state

256.6 -> and it would have some kind of behavior

259.052 -> which incorporates on its own.

261.015 -> Right?

261.8 -> So basically similar to that Java is programming language,

265.3 -> which is based on object oriented programming model.

268.6 -> So everything Java could be thought of as an object

272.569 -> or you define a class.

274.4 -> So say for example you have house right?

278 -> So house could be thought

279.9 -> of as an object or class rather a house has a class

283.8 -> and it would have certain attributes right

286.6 -> like number of rooms or stuff like that.

289.319 -> So that is nothing but the state of the house.

293.3 -> So this was actually brought in by Sun Microsystems in 1995,

299.1 -> and basically Java is nothing

301.4 -> but we have jvm but jvm is nothing but you kind

305.2 -> of kind of can say it's a specification right

308.7 -> Sun Microsystems has said that this is how it should be

312.585 -> so that any company tomorrow

314.551 -> I can go and create my own version of java,

317.5 -> but it has to be aligned to this particular specification

320.897 -> that is given by Sun Microsystems.

322.9 -> So Java is nothing but reference implementation

326.088 -> of java is provided by Sun Microsystems,

328.719 -> but nevertheless

329.834 -> as I said give him itself is a specification

332.743 -> which anyone can Implement actually but we will talk about

336.6 -> Sun Microsystems talk about the reference implementation

340.2 -> that is nothing but one created by Sun Microsystems.

343.525 -> So everything in Java would have a state

346.069 -> and behavior and which would be defined by class.

349.5 -> Again, it was started off by a team led by James Gosling

354.1 -> and we know it's open source,

356.2 -> which doesn't stop anyone from putting in whatever code.

359.833 -> I want to still we have lot of versions coming in Java.

363.4 -> So it's not that you just have one version

365.711 -> created by Sun Microsystems

367.368 -> and it's been used across the industry.

369.7 -> You have like find some issues or

371.7 -> if they want to have some kind of enhancement

374.491 -> in the open a particular module the keep doing it.

377.6 -> So right now we have like Java is at version 12,

381 -> which is like we have lot of enhancements coming in.

383.9 -> It's a evolving thing it's ever evolving thing.

387.2 -> And as I said, this is open source tomorrow.

389.979 -> If you become a good programmer in Java,

392.47 -> you could go and actually write something for Java

395.6 -> and which would be moderated by someone

397.835 -> and which would be put as open source.

400.2 -> And anyone can use it other thing is Java

403.8 -> the very important feature why we use Java

407.1 -> or why Java is so widely used is right once and run everywhere.

412.1 -> So you write a class or you write program once

415.308 -> and you compile it

416.575 -> and this particular compiled version of class.

419.703 -> Be run anywhere on any machine or you could transport

423.205 -> this particular compiled version of java,

425.9 -> which is nothing but classify we call it as a class file again,

429.8 -> you did not get into what is class file.

432.14 -> But just to say

433.022 -> that you compile it you get a compiled version of it

436.028 -> and this compiled version

437.5 -> of class could be transported anywhere in the network

440.783 -> or you could put it anywhere and just run it

443.5 -> so you could take it on your pen drive as well

446 -> and go anywhere

446.882 -> and plug your pendrive

448.242 -> get this class path download this class path

450.9 -> or download this class rather

452.882 -> and just run it so it right once and run everywhere

456.3 -> and the magic part is it could be run on any environment.

459.736 -> It could be run on any platform.

461.683 -> That's why it's platform independent.

463.833 -> So I could write a program today on Windows compile it

467.093 -> and tomorrow I can just take it on my pen drive and run it

470.6 -> on Linux as well.

471.9 -> So you don't have to take care about it.

474.2 -> Java by itself has a feature to make it platform independent.

478.7 -> So As you could imagine this is one of the reasons why

482.14 -> it's been widely used

483.572 -> because since we are getting into a phase

486.3 -> of distributed computing,

488.025 -> we cannot have everything run on same platform.

491.2 -> You don't know where your so you

493.1 -> as a programmer write something

494.65 -> but you don't know

495.607 -> where this particular program is going to run.

498 -> It could be on any platform.

499.7 -> So this is why it is more important.

501.829 -> So unlike dotnet, right?

503.111 -> You need to have Microsoft

504.551 -> just to give you this thing comparison

506.6 -> with dotnet so for.net you need to have

509.815 -> Microsoft stack implemented,

512 -> but for this you need not could be run everywhere.

516.3 -> So Java can be used to create complete applications

519.649 -> that may run on a single computer

521.672 -> or can be distributed

523 -> among servers and clients in the network.

525.311 -> As I said, this is more about the application

527.955 -> of platform-independent programming language.

530.544 -> So it could be used

531.64 -> on any machine you need not take care

533.758 -> about which machine your program is going to run on.

536.803 -> All right, so let's talk about Java.

539.646 -> Earth so what features do we have in Java?

542.8 -> First thing is Java is pretty much simple

545.876 -> when it comes to SDK

547.424 -> or when it comes to API application interface.

550.9 -> It's pretty much simple.

552.4 -> It's kept as simple as possible.

554.3 -> It's pretty much similar to other programming languages

557.4 -> and it's verbose.

558.5 -> So anyone can just read through it and understand

561.6 -> what it is trying to do

563.004 -> so they have kept it to that level so similar

565.617 -> to any high-level languages,

567.264 -> right the coach should be such that

569.1 -> as you read through it.

570.213 -> You should understand

571.2 -> what it is doing and that's what they have tried to do.

574.2 -> Its high-performance.

575.7 -> One of the things that I already mentioned about.

578.4 -> It's an evolving system.

579.935 -> It's not that it's been just done once and been used

583.11 -> throughout its evolving system.

585.027 -> So as and when this continuous Improvement done, right,

588.361 -> so as then when if I as the application programmer

591.508 -> if I find something not working

593.5 -> as expected I can raise a ticket

596 -> and they could go through the ticket

598.1 -> or there's a Java development.

599.8 -> Which has been driven by Oracle.

601.4 -> Now, they would look at the priority

603.235 -> of this particular stuff.

604.528 -> And if there are a lot

605.727 -> of tickets been raised by other companies as well.

608.4 -> And if something

609.219 -> could be done on the aspect on the particular aspect

612.237 -> that you raised they would surely Incorporated

614.9 -> and notify you

615.8 -> in a particular release the enhancement is coming up

618.8 -> and stuff like that.

620 -> So it's a evolving system and you know,

622.452 -> the performance is always

624 -> if there's some drawback or if there's something not working

627.1 -> as expected they

628.158 -> would surely Rectify it in the future releases.

631.8 -> So that way it keep it up to the mark the keep

635.261 -> the high-performance thing going it is secured.

638.8 -> So Java basically runs in virtual machine sandbox,

642.7 -> and no one can get into this particular space.

645.477 -> So no one can intrude it.

646.951 -> I would say

647.633 -> so that keeps it free from virus and stuff like that

650.8 -> or untrusted process.

652.4 -> And other thing

653.553 -> that is important is unlike C. Java doesn't expose

657.791 -> pointers so in see There could be malicious user

661.5 -> who could get into the memory location through pointers

664.807 -> and can manipulate the contents of a particular memory.

668.123 -> Right?

668.558 -> Whereas in Java.

669.7 -> It doesn't expose the pointer.

671.7 -> It doesn't give you the pointer to a memory location.

674.7 -> So you can't actually go and change the content

677.405 -> of a memory location when you are using Java

680.176 -> so that keeps it secure.

682.7 -> So it's robust.

684.1 -> So Java checks the code during compilation time and runtime.

688.178 -> So basically what happens is

690.136 -> as I said when you compile it you get a class file

693.559 -> and whenever you try to run this class file

696.493 -> on any of the machines,

698.029 -> it will ensure that it's properly done

700.5 -> or if there's some issue with the class file.

702.877 -> It would say that it's a correctly classify.

705.2 -> So basically you have some kind of checks done

707.847 -> during the compilation

709.141 -> as well compilation is nothing

710.694 -> but if you have something tactical error say, for example,

714.047 -> if you miss the semicolon at the end of a particular statement

717.5 -> or an end of any statement,

719.5 -> It would prompt you during the compilation time

722.064 -> that this is not what is expected or it

724.3 -> would ask you to correct it

725.906 -> once you have everything as for the expectation,

728.807 -> it would compile it and create a class file

731.4 -> and when you put this glass file to any of the machines

735.059 -> during the runtime it checks as well.

737.6 -> And the other thing is

738.894 -> about you don't have to take care about memory allocation

742.1 -> and releasing unlike in other programming languages.

745.473 -> Java by itself

746.4 -> does garbage collection garbage collection is nothing

749.4 -> but when a particular memory is not being utilized

752.5 -> by your program

753.5 -> of goes out of scope it would Java by itself has

756.7 -> a thread I don't want to get into threads

758.9 -> and stuff like that.

759.9 -> But Java would enough the memory contains by itself.

763.9 -> You don't have to explicitly write a code to clean

767.166 -> it and see you have to write a code to clean.

770.241 -> It errors in Java.

771.5 -> It's done by itself.

772.9 -> So that makes it robust other thing is it's portable

776.4 -> as we already spoke.

777.6 -> You can write a programming windows.

779.7 -> You can run the same program or you can write a program

782.6 -> in Windows compile it get a class file

785.038 -> or the compiled version of the class and just put it

788.4 -> on any platform.

789.761 -> It could be Windows.

791.3 -> It could be you run it on Unix or Linux or Mac

795 -> or anywhere so you don't have to take care about it.

798.231 -> So Java by itself does it

799.875 -> and that's where jvm comes into picture which we'll talk

803.494 -> about in the the further slides.

806.4 -> So other thing is it's Dynamic

809 -> which means that it has runtime polymorphism.

812.1 -> So all the objects are evaluated during runtime.

815.6 -> It's not just that it's done during the compile time.

818.447 -> There.

818.801 -> Is this something done during the runtime as well.

821.7 -> So basically it's called as runtime polymorphism.

824.9 -> But just to keep in mind not everything is linked up

828.011 -> during the compile time is something done

830.552 -> during the runtime as well.

832.9 -> So it could be distributed as well.

835.166 -> You don't have to have all the code put

837.621 -> into one machine and run it from my machine.

840.4 -> I could run something written on your machine as well.

843.755 -> If into net in the same network or if if they are exposed

847.3 -> to a network we could run programs on different machines.

851.6 -> So that's what distributed is all about.

853.922 -> So you could think of big data.

855.794 -> So this is one

856.684 -> of the major features why Java is been widely used

859.9 -> in big data, right?

861.3 -> So big data is nothing but you have chunks

863.9 -> of data you have like petabytes

866.12 -> of information coming in every minute

868.7 -> or every hour or every day,

870.8 -> right and you want to process it.

872.767 -> So it cannot be done in one machine

874.901 -> if you want to run everything on one machine

877.6 -> as we had earlier, right?

879.3 -> Everything was monolithic everything was done

882.1 -> on one machine sort of so that's

884.262 -> where you would want to have servers right.

887 -> Now.

887.8 -> The server thing is

889.2 -> it's not being used that much since there's a lot of English.

892.2 -> Intense stuff like that.

893.879 -> So distributed computing is nothing but we have

897.1 -> like pure computers or normal computers

899.902 -> that we have and programs are actually done

903 -> on this machines rather than rather

905.369 -> than having a high-end machines.

907.746 -> So basically this feature is

909.9 -> what helps Java to be used in big data.

913.6 -> And as I said,

914.66 -> it's run on commodity Hardware as against server Hardware

919 -> which needs a lot of investment for companies.

922.4 -> Java is multi threaded so multi-threaded is

925.974 -> nothing but so you have multiple cores on your machine,

929.8 -> right?

930.3 -> You have like four cores and stuff like that.

932.8 -> So you could utilize all this for course say for example,

936.2 -> you want to do addition of two numbers

938.404 -> and multiplication of two numbers right different numbers.

941.8 -> So you don't have to run everything on One Core.

945.138 -> So this could

946.018 -> since you have four processors right for course,

949.2 -> you could have addition run on one core

951.6 -> and you could have this multiplication going on

954.2 -> at the same time at the same instance, right?

956.84 -> You could have this multiplication going on as well.

959.864 -> You could run them as a thread right?

962 -> You don't have to have one waiting for other.

964.7 -> You don't have to do it in a sequential manner

966.996 -> when you're operating on different variables, right?

969.6 -> So that's what multi-threaded is all about.

972.3 -> As I said you could have this operations carried out

975.3 -> on different course in the same instance of time.

978.9 -> Object-oriented again as I spoke earlier,

982.6 -> everything is performed using objects and Java

986.019 -> can be easily extended

987.691 -> since it is based on object model.

990.684 -> Now, let's talk about which sectors

993.3 -> or which industry sectors actually use Java.

997.5 -> So you have Android apps.

1001.007 -> So Android apps Cal could be written on Java.

1004.6 -> So basically the underneath is Android API,

1007.7 -> which is similar to jdk so jdk is nothing

1010.6 -> but Java development kit.

1012.4 -> It's widely used in financial services industry.

1015.533 -> If if you would have some idea about it.

1018.283 -> You could see

1019.2 -> that mostly all Financial companies use Java.

1022.4 -> So the Legacy systems

1023.853 -> that we have in financial companies is mostly

1026.9 -> developed on Java.

1028.423 -> So one of the aspects for this is more

1031.269 -> about it's pretty secure.

1033.192 -> So that's why it's been written on Java lots

1036.5 -> of global investment Banks.

1038.5 -> Like Citigroup Barclays Standard Chartered and other Banks

1042.453 -> use Java for writing

1043.84 -> front and back office electronic trading system.

1047.1 -> So one of the main features why it's been used

1050.5 -> in financial industry is about security.

1053.5 -> It provides high level of security

1055.8 -> as we spoke earlier Java web applications.

1059.1 -> So basically you have web servers on which

1062.02 -> your application would be hosted

1064.3 -> and you could request for a particular JSP

1067.5 -> or JSP is nothing but a dynamic HTML page right there

1072.4 -> in the contents could change basically you could request

1075.9 -> for some particular JSP

1077.3 -> and you could get it so say for example,

1079.56 -> you are trying to log on

1080.993 -> to a particular application you get a login page

1083.9 -> that is nothing but a JSP.

1085.9 -> So basically a mini of the web applications

1088.7 -> is developed on Java as well.

1091.3 -> One of the main features why web applications are developed

1094.476 -> because you have a lot of web servers supporting,

1097.3 -> Java you Have to deploy application

1100 -> on a particular web server

1101.8 -> and could access it from anywhere across glue.

1104.7 -> You should be on internet though.

1107.3 -> Embedded system when it comes to embedded system.

1110.539 -> It has to be lightweight, right.

1112.8 -> So Java it I remember Java version 8 had lot

1116.9 -> of feature making it pretty much light weight when it comes

1120.543 -> to embedded systems.

1122.1 -> So basically you have Micro addition j2me.

1126 -> What we are talking here is j2se and the thing

1129.5 -> that we so there are three flavors of java.

1133.2 -> So one is j2se,

1135 -> which is nothing but standard edition

1137.1 -> and which is standard edition,

1138.984 -> which you have like all the data types and stuff

1142.039 -> like that all four loops and stuff like that.

1144.9 -> Right that is about j2se.

1147.6 -> You have G to EE which is Enterprise Edition,

1150.765 -> which is nothing

1151.565 -> but the web application that we spoke about and we have j2me

1156.684 -> which is micro Edition,

1158.761 -> which is nothing but for embedded systems

1161.846 -> as its name suggests, it is micro Edition,

1165.6 -> which is light in weight.

1167.7 -> And as we can imagine that in embedded system,

1170.921 -> it has to be lighter since it is burnt into a chip,

1174.5 -> right and you cannot have a big application.

1177.7 -> So that's why we have lightweight

1180.1 -> when it comes to j2me.

1183 -> So again as I touch base on this it's about web servers

1187.243 -> and application servers

1189.153 -> which makes Java compatible for web applications.

1193.4 -> So we have Apache Tomcat

1195.2 -> which is pretty much widely used which was a web server earlier.

1200.1 -> Now, they have Apache Tom e or which is Tom double e

1204.761 -> which is nothing but application server version of it.

1209.1 -> So basically when it comes to web servers

1212 -> or application servers,

1213.836 -> what you do is you

1215.23 -> as a client could send a request to our web server

1219 -> and web server

1220.2 -> or the application server would just process

1222.936 -> this particular request

1224.4 -> and send the response the way the It's written.

1228.2 -> So basically it would serve the expected result out.

1232.4 -> So you have Enterprise applications.

1235.4 -> Again, this is Java Enterprise Edition,

1238.323 -> which makes it favorable for web applications.

1242.438 -> So all these specifications j2me.

1244.9 -> J2w.

1245.8 -> J2se, this are nothing but specifications exposed by Java.

1250.6 -> So if you as a developer wants to do something

1254.1 -> or if you want to write your own version of it you can do it.

1257.976 -> So where is Java used again scientific applications?

1263.1 -> So I as you could imagine in scientific applications,

1266.74 -> you need to have high level of accuracy

1269.4 -> and precision rather.

1271 -> They could be mathematical equations

1273.4 -> and mathematical computations which needs lot of CPU time

1277.6 -> because it's very CPU intensive right?

1280.1 -> When you do a very precise calculation

1282.6 -> with high level of high degree.

1284.819 -> It needs lot of CPU time, right?

1287.5 -> So that's where Java is good at.

1290.738 -> So basically this is about as a spoke about multi-threading

1295.2 -> utilizing all the course to the fullest suppose.

1298.7 -> You have four core processor using all these four cores

1302.7 -> is been done by Java Java has feature

1305.6 -> or through threads you could actually read through

1309.023 -> or actually utilize this

1310.7 -> for course to the fullest Big Data Technologies again,

1315.5 -> big data is nothing.

1316.735 -> But as I said,

1317.6 -> it's distributed you cannot have everything run on one machine,

1321.3 -> which was the case earlier.

1322.9 -> You would have one server put up

1324.7 -> and everything is done on that particular server.

1327.4 -> Now, it cannot be the case.

1329.4 -> That's where Big Data comes into picture wherein you

1332.4 -> have distributed architecture

1334.005 -> and you have this data

1335.333 -> being processed across Network rather than just on one machine

1339.007 -> and mind you as I said,

1340.471 -> this machines are commodity hardware

1342.7 -> and not server level Hardware

1344.6 -> or the Enterprise level Hardware

1346.4 -> which makes Cheaper Internet of Things So Internet

1351.6 -> of Things is coming up

1353.152 -> the booming thing wherein you could connect things together.

1357.317 -> Say, for example, you have cars, right?

1360.5 -> So you could connect cars together

1363.3 -> so you could have sensors in your car

1365.506 -> which could emit data and you could connect them together.

1369 -> So basically it's all connecting things together or say,

1372.639 -> for example, let me talk about internet itself.

1375.6 -> So earlier if you remember computers were not connected

1379.8 -> it were all pure right.

1382.5 -> It could just be used for your own purpose.

1385.7 -> Now internet has started

1387.2 -> wherein you have all these computers connected

1389.737 -> and if you are connected to the internet,

1392.011 -> you could go onto Google and search something

1394.6 -> or whatever you want to sort of

1397.1 -> So basically this is what internet of things is all about.

1401.13 -> So consider this instead of computer.

1403.714 -> It could be any other objects a car for example,

1407.17 -> as I said so consider car has sensor

1409.658 -> and it is emitting this sensor data every minute

1413 -> and we could utilize this sensor data

1415.571 -> and do something with it or one car

1418 -> can know where the other car is.

1420.7 -> So that's what internet

1422.1 -> of thing is about all about connecting things together.

1425.819 -> Let's start off with the setup setup for Java.

1429.8 -> So basically you could go to this particular site

1432.5 -> and just download the SDK based on this jdk, right?

1436.8 -> So basically based on whatever platform you are at.

1440.2 -> If you are using Windows,

1441.5 -> you have to select Windows if you are using something else

1444.3 -> if you have mac, you can select Mac.

1446.4 -> So this is pretty much similar

1448.3 -> to other softwares you get an exe file download it

1452 -> and you just have to run that exe file.

1455.6 -> So basically I can show you what gets downloaded.

1460 -> So I have downloaded version 12 for Java

1462.947 -> as you could see here and and since its Windows,

1466.5 -> it is mentioned as Windows.

1468.231 -> So this is nothing but an exe file that you get

1471.1 -> which you could run

1472.329 -> and you would have Java installed on your machine.

1476.16 -> So it's pretty simple.

1477.662 -> It's pretty much similar

1479.3 -> to other software's you have say for example,

1483 -> or I could just show you the location

1485.172 -> where it is installed.

1486.5 -> So if you get into the program files,

1489.1 -> you can see javabean installed here, right?

1492.4 -> And it says jdk 12.

1493.9 -> So once you install Java,

1495.656 -> once you download this particular stuff jdk and

1498.782 -> once you install this this executable you

1501.6 -> should be able to see this Java folder

1504.045 -> in your program files.

1506.1 -> So it shows here.

1508.8 -> It's for you can select whatever you want to see you have

1512.318 -> as you could see here.

1513.7 -> This line X there is Windows Mac OS

1515.84 -> and stuff like that.

1517.1 -> You have to select the platform you are

1519 -> on and should be good to go.

1521.5 -> This is done.

1522.422 -> You could see you get a exe which you have to run.

1526.38 -> So basically to run Java what you have to do is

1530.3 -> yeah.

1531 -> So you go to the system you have control panel system you go here

1535.7 -> and you have to click on Advanced system settings.

1539.3 -> Basically, what we are trying to do is we are going to set

1542.4 -> an environment variable right

1544.3 -> and what we are going to set is this path variable.

1547.6 -> So you have

1548.5 -> if you want to put it specific to a particular user you

1552.062 -> can put it here put it in the upper space

1554.638 -> or you want it across the system.

1556.7 -> You could basically put the path variable here

1559.472 -> in the system variables.

1561 -> So once you install it you have to make sure

1563.759 -> that you have this particular

1565.62 -> path being put in your path environment variable.

1569.1 -> So basically tells the OS

1571.023 -> that you have executables within this particular directory.

1577.6 -> So once that is done,

1579.88 -> once you have this properly setup,

1583.203 -> let me open a partial.

1585.8 -> So partial is nothing but it's

1587.3 -> pretty much simpler to command prompt

1590 -> but it's a Linux flavor of it.

1592.615 -> So basically you could run Linux commands as well.

1596.961 -> Okay, so I will I will once this is done.

1600.3 -> Give me a second.

1602.5 -> Okay.

1603.1 -> So with partial you can do LS

1605.8 -> which would give you a listing unlike in command prompt.

1609.6 -> You have to give dir.

1611.238 -> So it's basically good for programming.

1614.5 -> So once you have this properly set

1617.3 -> once you have this path properly set

1619.7 -> if you write Java here,

1621.246 -> if you write Java on your command prompt,

1623.937 -> you should be able to see this help coming up here.

1629 -> So if it's not properly set up,

1630.9 -> you won't see this it would give you unrecognized command.

1635.6 -> Yeah, open command prompt and type Java.

1638.3 -> So once the path is properly set you should be able to see this.

1643.1 -> So let's set up Eclipse as well.

1645.9 -> So it could be eclipse

1647.4 -> or IntelliJ whatever you are comfortable

1650.14 -> with so you could use either of them

1652.6 -> since IntelliJ has much more features.

1655.3 -> You could use IntelliJ as well.

1657.8 -> So you go to Eclipse download

1661.2 -> and whatever flavor you can take the latest one

1664.4 -> Whatever flavor you want to install

1666.1 -> if you if you want a simple one you can do it.

1668.869 -> If you're trying to do something on web.

1671.269 -> You can download that one as well.

1673.3 -> So basically for simple purpose

1675.473 -> for whatever we are going to do you can have normal ones.

1679.8 -> So let me quickly open up my so this is nothing

1683.5 -> but the IDE integrated development environment

1686.961 -> that I use with just IntelliJ

1689.7 -> all the IDS are pretty much similar.

1692.365 -> So IntelliJ similar to Eclipse, so it's coming up.

1697.4 -> So basically what you do is

1699.13 -> you have to select a workspace first workspace is nothing

1702.576 -> but all your program

1703.85 -> all the class files all the class and everything

1706.843 -> that you write would be put into this particular Works piece

1710.7 -> and you can create a new class and start off.

1713.8 -> So when we get to the hello world program,

1716.4 -> which is the first program that we are going to talk

1718.8 -> about it would give you a clear idea

1720.8 -> on what we are talking about.

1723.3 -> So let's talk about Java internals

1726.7 -> how it looks like

1727.892 -> and all the features that we spoke about.

1730.7 -> So basically so far

1731.919 -> what we have covered is more about Java is object

1735 -> oriented program or it uses object-oriented programming.

1739.3 -> Paradigm which is nothing

1740.995 -> but everything is thought of as a class with a particular State

1745.2 -> and behavior right is platform independent.

1748.5 -> That's why it's been widely used it secured as well.

1751.62 -> That's why it's been used in banking applications and stuff.

1755 -> It's good for distributed computing

1757.2 -> since its platform independent.

1758.936 -> You don't you just have to write it once

1761.035 -> and you can run it everywhere.

1763.1 -> So basically this platform independent aspect is

1766.864 -> what helps it to be widely used in Big Data applications.

1772 -> So let's talk about the internals.

1775.1 -> So what is jvm jvm is nothing.

1777.7 -> But again, it's a specification right?

1780.546 -> You could have your own jvm son

1782.95 -> by itself gives specification for a jvm.

1786.1 -> This is what the GBM should be all about so

1789.33 -> I could create my own jvm.

1791.4 -> But we usually we use the reference implementation

1795 -> of sun Microsystems Oracle now.

1798.8 -> Right, so jvm is a virtual machine

1802.1 -> that runs the bytecode.

1804.1 -> So basically there has to be some level of compilation done

1808.4 -> before give him can understand it.

1811 -> So that's where you have Java compiler.

1813.849 -> And so what this does is nothing but it takes your source code.

1818.474 -> It takes the class files as or it takes the class

1822.282 -> that you write

1823.359 -> as is so Java compiler would consume it

1826.3 -> and kind of compile it into a DOT class file so

1830.3 -> dot class file is nothing but compressed version of it

1833.467 -> and compiled version of it as well.

1835.8 -> And this dot class file is

1838 -> nothing but it's also known as bytecode and this is

1843.082 -> what a jvm could understand.

1845.4 -> So once you have this class file,

1847 -> it could be sent to the jvm

1849 -> and jvm could understand it and run the applications.

1852.813 -> So what makes Java platform independent is

1855.967 -> this Java compiler is platform.

1858.2 -> Pendant you don't have to take care about it.

1860.4 -> You just have to run the compiler.

1862.3 -> And whenever you want to run this particular byte code

1866.2 -> on any of the machines,

1867.969 -> you just have to have jvm for that particular machine.

1872.5 -> Right?

1873.3 -> So basically if you want to have online X,

1876.3 -> right if you want to run it on Windows,

1878.7 -> you would have jvm installed on Windows

1881.393 -> or you would download the jvm for Windows.

1884.3 -> And if you want to run it on Ubuntu or the Linux

1887.911 -> or Mac would just have to have the jvm downloaded

1891.6 -> for that particular platform

1893.6 -> and it should be able to sense this particular byte code.

1897.6 -> So basically this is what makes it platform-independent.

1901.476 -> Right?

1901.9 -> As I said, once you have this bytecode

1904.2 -> once you compile it this bytecode could be transported

1907.317 -> or ported into any

1908.324 -> of the machines in operating systems

1910.217 -> and you should be able to run it

1912.1 -> that is what it is all about.

1913.8 -> It's right ones and run anywhere.

1916.2 -> So as I earlier mentioned you could

1918.5 -> As get this class file into your pen drive

1921.6 -> and take it anywhere

1922.9 -> and you could just plug your pen drive

1925 -> and just run through

1926.181 -> that's how simple it is.

1928.1 -> So, this is Java runtime environment where

1931.5 -> in you have set of jvm plus you have libraries libraries,

1937.2 -> it does nothing

1938.003 -> but you know,

1938.7 -> although programs put together all the programs source code

1942.2 -> for Java put together.

1943.7 -> So our T dot jar is one of the libraries

1946.279 -> which would have most of the classes

1948.663 -> or you have you till classes maybe string class string

1952.772 -> is a class itself,

1953.997 -> which is exposed by Java.

1955.8 -> So this particular jar file

1958.6 -> or it's a Java archive jar is nothing but Java archive

1963.4 -> which is set of java classes or the class files rather

1967.092 -> which would have lot of class files within so

1970.1 -> in our T dot jar you would have something like string class

1974 -> and stuff like that a lot of other classes,

1976.7 -> which is been used by the sea.

1978.5 -> Some are which has been used by Java itself?

1981.412 -> So basically in JRE this is

1983.523 -> what you have jvm plus set of libraries

1986.446 -> plus other additional files.

1988.6 -> So as spoke jvm is nothing but specific to environment,

1992.6 -> but all these things like Artie dot jar

1994.961 -> and stuff like that would be independent GRE

1997.666 -> does not contain tools

1999.133 -> and utilities such as compilers

2001.2 -> or debuggers for developing applets and application.

2004.612 -> So GRE by itself the runtime environment,

2007.288 -> so it doesn't have compilers and stuff like that.

2011.4 -> So jdk is nothing but it specifically

2014.584 -> for development you could see here.

2017.2 -> It's JRE plus development tools you have compilers

2021.4 -> and stuff like that as well.

2023.6 -> So to run a class file,

2025.4 -> you just need the JRE but if you are a developer,

2028.8 -> you would need jdk so what we downloaded earlier

2032.211 -> if you remember

2033.3 -> that was jdk right jdk for Windows or jdk for liners.

2038.3 -> So basically if you see this one could see here as jdk.

2043.1 -> So essentially you need jdk only if you are a programmer

2046.999 -> if you just want to run the class file GRE would suffice

2051.4 -> so why is jdk GRE and jvm

2054.5 -> as we spoke about you could see jdk is a superset.

2058.6 -> It has everything right GDK would have your jvm.

2062.8 -> Plus it would have as we spoke here.

2066.6 -> It's JRE plus your development tools as well.

2071.7 -> As you could see here details it has everything here.

2075.9 -> It would be really confusing right now.

2078.8 -> If you directly get into what all this is all about,

2082.4 -> but basically you could imagine jdk is a superset

2085.9 -> and Jerry is nothing but it's your runtime environment

2090.176 -> which has jvm and some additional files

2093.2 -> or RT dot jar

2094.5 -> as we said

2095.307 -> which is nothing but set of files set of class files

2099.1 -> that is exposed by Java

2100.8 -> which could be used like string for example,

2103.822 -> right?

2104.8 -> Let's see how it works.

2106.195 -> So basically you have your source file.

2108.542 -> So this is what a developer would typically right

2111.6 -> would create a DOT Java file.

2113.5 -> So whatever you write you create a class.

2116.5 -> You just create a new class and write something to it.

2119.757 -> What you get is dot Java you get the extension dot Tower.

2123.2 -> So basically this is your source code,

2126.022 -> whatever you write you

2127.654 -> as a developer would write this class.

2130.4 -> Is would be sent for compilation or whenever you are good enough

2134.6 -> done with your coding you would compile it.

2137 -> And once the compilation is done once everything

2140.037 -> looks good enough.

2141.223 -> Once the compiler

2142.295 -> doesn't Mark anything and doesn't flag anything rather,

2145.7 -> which means everything is syntactically, right?

2148.6 -> You will get Java bytecode.

2150.48 -> Just nothing but dot class 5.

2152.9 -> Now.

2153.1 -> This dot class file could be moved across Network

2157.2 -> or you could as I said,

2159 -> you could just put it in your pen drive

2161.4 -> and can take it anywhere

2163.2 -> and you could run it on any of the environments.

2166.548 -> You just have to have jvm.

2168.327 -> So basically you could run this class file,

2171.2 -> which is compiled on Windows.

2173.04 -> You could run it on any

2174.5 -> of the environment any of the platform's.

2177.5 -> So this is something that we spoke about during runtime.

2181.145 -> There's a verification as well.

2183.2 -> So so when classloader would load this particular class file,

2188.3 -> it would ensure

2189.4 -> that it is up to the Mark or it's not manipulated

2192.8 -> sort of so if it all it sees something wrong,

2196.3 -> then it would flag it off

2197.979 -> as you know corrupted file or something.

2200.8 -> So this is nothing

2202.138 -> but Java class file libraries are T dot jar that we spoke

2206.5 -> about Java archive.

2208.1 -> So this is what is happening.

2209.952 -> When you run a particular class five, right?

2212.8 -> So you have this class loaded and then you have this compilers

2218.1 -> just-in-time compiler actually running it for you.

2221.4 -> So basically the part of jvm so jvm is remember jvm is nothing

2226.1 -> but it's a platform.

2227.511 -> It is specific to platform.

2229.417 -> So basically for Windows you would have a different jvm.

2233.22 -> And for line X you would have a different jvm.

2236.457 -> So yeah, you get this class

2238.4 -> you load this class using class loader

2241.1 -> and you run through the application or run

2243.938 -> through the class files.

2246.2 -> So typically this is

2247.588 -> how Java operates so just to give a just on this one.

2251.2 -> So you have a source code you have dot Java file written

2254.6 -> you compile it you get our class file

2257.1 -> and you can put this class file anywhere.

2259.7 -> You can run this class file anywhere on your network

2262.594 -> or wherever you want to you just have to take this class file

2266 -> and on the machine on which you run.

2268.4 -> What would happen is

2269.8 -> you load this class file first using class loader

2273.4 -> and with jvm jvm would have just-in-time compiler

2277.026 -> which would run a particular class for you.

2280.3 -> Right?

2281 -> So what we are trying to do here is you're running

2283.9 -> the source code

2284.7 -> that's written on any environment you are running it

2287.7 -> on any other environment.

2289.078 -> So basically you could write this on Windows.

2291.564 -> You could write source code on Windows,

2293.8 -> but you could run it on say for example line X.

2296.6 -> So that is what makes it platform independent.

2299.9 -> So here let's create one class

2303.3 -> and as we created I will More about it

2307.2 -> so that you could open up your eclipse

2310 -> and could create something like a new project

2314.6 -> so it could be a bit different for you the look

2317.8 -> and feel might not be exactly the same as mine,

2321.006 -> but you just have to create a new project select Java.

2324.7 -> So basically I could a project name.

2327.392 -> So whatever you want to so basic nomenclature is

2331 -> like it has to start with uppercase letter,

2333.9 -> which is camel casing right?

2335.8 -> So you should follow camel casing venue.

2338.3 -> That's one of the best practices

2339.9 -> it won't flag you as some error or something,

2342.5 -> but that's a normal industrial practice that

2345.6 -> whenever you create a Java project.

2347.95 -> It has to use camel casing created record, Java.

2353.3 -> So it's creating a project for me.

2355.6 -> And as you can see here,

2357.6 -> I have this particular project being created right now.

2361.9 -> What I do is I create Java class.

2365 -> So basically as we

2366.6 -> said everything could be seen as a class,

2369.861 -> right that's what object-oriented is all about.

2373.5 -> So basically what I would do is I would create a class here.

2378.6 -> So this is my source folder

2380.6 -> where enormous Source class would be there.

2383.9 -> So as you can see here new Java class so say

2388.2 -> I create calm dot Ed u-- Rica.

2391.6 -> So this is nothing but your name space

2394.446 -> or the package, right?

2396.5 -> So you could give whatever you want to basically this is

2400.121 -> to avoid collisions, right?

2401.9 -> If we don't have a name space there would be lot of collisions

2404.999 -> within the class.

2406 -> So there are a lot of people working

2407.9 -> on the same project right so I could create a class with name.

2412.1 -> Class A and the other person might read classy as well.

2416.8 -> So when this is club together into one particular application

2420.563 -> there would be Collision So to avoid this basically

2423.7 -> what you have is

2424.9 -> you have a namespace.

2426.234 -> So I would write as calm down dear a card dot Class A.

2429.6 -> The other person would write something else

2432.1 -> and that would avoid class name collisions Applause collisions.

2436.7 -> So this is compounded Eureka is my package

2440.3 -> or namespace and hello world is my Java class name.

2447.9 -> So as you could see here,

2449.803 -> there's a package calm down Ed Eureka,

2452.62 -> which is again a namespace

2454.6 -> and there's a class by name hello world that's been created.

2458.804 -> Right?

2459.4 -> And if you want to see you could actually go

2462.807 -> and so you can see a folder structure

2465.6 -> created here in the source.

2467.246 -> So this is your Source folder right within your project.

2470.6 -> There was a source folder where in we created the class.

2473.637 -> So if you go

2474.3 -> to the source folder you could see a packet structure

2476.9 -> or you could see a directory structure being created

2479.8 -> which starts with calm

2481.1 -> and within calm you would have at Eureka

2483.5 -> and here you can see Hello World dot Java.

2486.307 -> So remember we said

2487.553 -> that your source code would have all the Java files.

2490.9 -> So basically this is what I was referring to.

2496.3 -> This is a method

2497.4 -> that the default method that's been called.

2500.031 -> So when you run this particular class file

2502.6 -> jvm would actually look out for this particular method.

2506.7 -> So you need to have the same signature

2509.176 -> as has so you would have a main

2511.251 -> method wherein your program execution would start, right?

2515 -> So as then when you compile it and run the class file,

2519 -> so basically when you compile it you would get a class file,

2522.2 -> right and when you run

2523.8 -> this class file jvm would check out for this main or a method

2528.236 -> that has the same signature as this one.

2530.988 -> That's a main method

2532.4 -> and your program execution would start running from here.

2536.2 -> So basically it's a entry point for your execution, right?

2540.4 -> So this would be

2541.577 -> a simple program wherein we would just print hello world.

2546.084 -> So basically you have

2547.7 -> like system system is a class and this is

2551.035 -> how you print in Java.

2553.3 -> So I don't want to confuse right away by saying

2556.64 -> what is system worries out and println,

2559.43 -> but basically what you have is a system is a class

2563.2 -> as I said everything Could Be Imagined as a class.

2566.587 -> So in Java everything is a class.

2568.9 -> So basically you could just click here

2571.3 -> and you could see the source code of it, right?

2574 -> This is the source code and this is coming

2576.3 -> from our T dot jar remember in jvm.

2579.2 -> We spoke about in GRE.

2581.1 -> We had our DDOT jar.

2583.5 -> We had Jerry we had jvm plus plus class files.

2587.8 -> So all this has been written by Java by the Java community.

2592.1 -> So basically you can see here.

2594.3 -> This system itself is a class.

2596.5 -> So out is instance variable

2598.7 -> and println is nothing but a method within out so

2603 -> what this statement particular thing is going

2605.699 -> as nothing but writing it on to your console.

2608.5 -> So let's print hello world.

2613.2 -> So basically when you build a project it's compiling it

2616.645 -> as you could see here.

2618.049 -> It's saying it's building it.

2622.834 -> So once it has built it you could see a class file here.

2627.1 -> Right?

2627.9 -> So you could see here hello world dot class.

2631 -> This is because we built it when you build it.

2635.2 -> Your Java file would be compiled by your compiler

2639.4 -> and it would create a DOT class file.

2641.3 -> And remember as I said,

2643.2 -> this class file dot class file could be run on any machine.

2647.4 -> So this is Windows machine

2649.334 -> that have written this file Java file

2652.064 -> and compiled on now.

2653.531 -> This dot class file could run on Linux or any platform

2657.419 -> that you want to run it on.

2659.7 -> So, let me talk about this class.

2661.823 -> Right?

2662.6 -> So you have a public key word,

2664.677 -> which is nothing but access modifier

2667.1 -> which gives visibility.

2668.7 -> So basically what we are trying to say here is hello world is

2672.545 -> publicly could be publicly seen

2674.531 -> so it could be seen anywhere within the application.

2677.8 -> So basically for class level you have public which

2681.369 -> as the name suggests.

2682.9 -> As the name gives out it could be seen anywhere

2686.166 -> within your application

2687.8 -> that the visibility key access modifier.

2690.7 -> All right, so you have the keyword class here,

2693.8 -> which is for the class.

2695.2 -> You need to have it mentioned as class.

2697.4 -> If you write something else,

2698.8 -> then it would give you a compilation error.

2701.3 -> So it has to be exactly the same.

2703.6 -> All right, that's the syntax of it.

2705.7 -> Hello is nothing but the name of your class,

2708.7 -> then you have this public static void main,

2711.4 -> which is nothing but as I said,

2713.3 -> this is the entry point for your application

2716.212 -> or your class file.

2717.5 -> So when you run this particular class,

2719.594 -> it would start off from here.

2721.3 -> You have a static keyword static keyword is nothing

2725.1 -> but it's at the class level.

2727.21 -> So basically you need not create instance.

2730.3 -> We haven't reached that point yet.

2732.5 -> So basically hello is a class

2734.8 -> and you could create instance of hello,

2737.4 -> which is nothing but object right?

2739.889 -> So when you have a static keyword here

2742.705 -> You need not create object of hello to run it

2746.09 -> if it's not static,

2747.638 -> then you need to have object of hello created.

2751.1 -> So basically what I'm trying

2753.253 -> to say is see you have one more method here,

2757.6 -> which is test.

2760.2 -> Now this doesn't have a static keyword here.

2763.3 -> So basically what we can do is we can print So

2772.297 -> yeah, this is a non-static method right now.

2775.8 -> We cannot call it directly.

2777.9 -> If it's a non-static.

2779.26 -> You need to have a instance of Hello World created.

2782.51 -> So basically how you create instance is nothing

2785.5 -> but hello world.

2786.73 -> That's your hello world object.

2789.5 -> So when I say instance I'm talking

2792.1 -> about creating object, right

2795 -> and you could create new hello world.

2798.5 -> So object of hello world is created using new keyword right?

2803.8 -> When you do this you would get object of it or now.

2808.3 -> What I do is so basically

2810.3 -> what I was trying to say is you cannot call test

2813.6 -> as is if you do it you would get a compilation error saying

2817.625 -> that non static method test cannot be referenced

2821.3 -> from a static context, right?

2823.4 -> You cannot call it without having your object.

2826.9 -> So basically I can call it

2828.9 -> on Hello World object DOT test Now I can call it now.

2833.4 -> It doesn't give me compilation error.

2836 -> I'll create one more static method

2838 -> which would give you some idea.

2841.4 -> So I will rename this as non static test

2845.9 -> and this would be static test.

2849.946 -> Right and we are printing your static method

2853.6 -> and here we are printing non static method.

2856.9 -> So hello world dot nonstatictest.

2861.1 -> Now, whereas the static test did not be called using object

2865.9 -> so we could directly call static test.

2869.6 -> Sorry, I haven't written static here.

2872.4 -> So this is a static method.

2875.5 -> Okay, so now you could see here.

2879.546 -> It compiles fine.

2881.7 -> Right?

2883 -> So what I was trying to say is

2885.3 -> when you have a static method you do not have

2888 -> object to call it.

2889.147 -> Whereas non-static method you need to have object.

2892.269 -> That's what the static is all about.

2894.475 -> Then you have void is nothing but the return type

2897.5 -> it's not returning anything from here.

2899.676 -> So that's why it's void.

2901.088 -> You have main method.

2902.323 -> That's the key word

2903.441 -> that the entry point for your application.

2905.7 -> You have this arguments.

2907.684 -> You can see string array of strings

2910.3 -> which are arguments provided to a particular program.

2913.4 -> So you could pass on as many arguments

2916.196 -> as you want or if your program is say,

2918.9 -> for example,

2919.769 -> you want to pass your name as an argument you can do that.

2924.2 -> So this is arguments then we

2926.9 -> have main which represents the Above the program

2930.046 -> which I already mentioned then

2932.135 -> we have system dot out dot println is nothing

2935.2 -> but the print statement

2937.1 -> so as I mentioned system

2938.527 -> is nothing everything could be thought of

2940.993 -> as a class system is a class out is instance variable

2944.2 -> and println is a method within out.

2946.8 -> So basically you don't have to think much about it just

2950.047 -> to understand the structure of it just to understand

2953.178 -> how a particular class is been written.

2955.511 -> This is what we have.

2956.8 -> This is how we write a class right again,

2959.8 -> just to brief on this you have access modifier

2963 -> which denotes the visibility of a particular class.

2966.5 -> You have the class name you have the main method which is nothing

2969.841 -> but the entry point

2970.972 -> for your class you have a static method,

2973.315 -> which says whether you need

2975.023 -> an object to call a particular method

2977.3 -> or could be called directly from a class.

2980.005 -> You have a return type here.

2981.9 -> So this is how typically any method would be written

2985 -> and you can write

2986 -> whatever statements you want to within this particular method.

2989.389 -> This case we have printed out hello world.

2991.9 -> So basically you could follow this

2994.1 -> when you do it on Eclipse,

2996.4 -> so it might be a bit different based on the eclipse version

3000.146 -> that you would have

3001.374 -> but it should be pretty much similar.

3004 -> All right, so you create a new Java project.

3007.7 -> So I showed this already on IntelliJ,

3010.8 -> which is also widely used IDE.

3013.9 -> But yeah, you could use Eclipse as well.

3016.4 -> So basically you

3017.414 -> could see the project name being written as hello world,

3021 -> right and here it mentions the JRE to be used.

3025.6 -> So here you can see class class being created and let's see

3030.687 -> how we can run this.

3033 -> So we compiled it and we saw that dot class file was created.

3038.13 -> Now we can run this.

3039.9 -> So as I said main is the entry point

3042.7 -> so it would start running from here.

3045.2 -> So your program control would come here.

3048.1 -> And the first thing

3049.273 -> that it would see is you have printed hello world,

3052.3 -> so it should print this one then I would keep it simple.

3056.235 -> I don't want to let's see what's been printed here, right?

3061.1 -> So you could see here.

3062.5 -> Hello world being printed first, right?

3064.9 -> This is where the program execution started from.

3068 -> So it came to mean so hello world it printed

3071.556 -> out hello world.

3073 -> Then you give a call to this non static method.

3076.607 -> So it printed non-static method

3079 -> which is been printed in this particular method

3081.9 -> and then it gave a call to static method

3084.9 -> and you could see static method being printed here.

3088 -> So one thing to remember is the program execution starts

3091.8 -> from Maine and it just you know executes this main method.

3096.1 -> So whatever content you want to write you

3098.1 -> would basically write it in the main method

3101.488 -> so you could see here hello world being printed out.

3106.4 -> Let's see how easy it is to coat the same in the J shell.

3111.2 -> So J shell is nothing but shell prompt

3113.939 -> that was created

3115.124 -> in Java version 9 since nine you would have gesture.

3119.1 -> So since I have Java version 12,

3122.3 -> I should have J shell as well.

3128.9 -> So yeah, J shell is nothing but a prompt

3132.8 -> so it's nothing but instead of writing

3135.15 -> into integrated workspace.

3136.8 -> You could have J shell

3138.082 -> and you could pry out something here.

3140.2 -> It's not something for production use

3142.3 -> as such it's basically

3143.83 -> to test something right you as a developer could

3147.165 -> if you want to see what

3148.7 -> it does instead of writing everything into the main.

3151.83 -> So if you write a class you

3153.305 -> would have to write things into the main

3155.607 -> and then run it and stuff like that with J. Shell.

3158.5 -> It's just a kind of interpreter wherein we could write something

3162.144 -> some command and see what the output is.

3164.6 -> So basically you could say for example we printed hello world,

3168.8 -> right so system dot out Dot println.

3174.6 -> Hello world, right if you remember this is

3177.7 -> what we typed into our main method plate.

3180.7 -> So if you want to run this you have to have

3183.8 -> all this artifacts created

3185.533 -> as is right to have a class you need to have main method

3189.214 -> and then build the class

3190.886 -> and then run it basically initial you could run it

3194.3 -> just to see what's output.

3196.7 -> As I said,

3197.379 -> this is not application as such this is just

3200.3 -> for the developer to test

3202.046 -> what the output for a particular command would be

3205.6 -> and what a modifiers in Java.

3208.3 -> So one thing

3209.4 -> that we saw in the program was access modifier.

3212.9 -> We already saw about actually this one right public

3216.233 -> and these are public here as well.

3218.5 -> So these are nothing but modifiers right public

3221.643 -> as I said this public means the access modifier which shows

3225.5 -> that hello world

3226.528 -> could be accessed anywhere throughout your application.

3230.1 -> So here we can see as a board or the fries changes.

3233.533 -> Meaning of other phase in some so basically it

3236.533 -> just trying to say that one of the aspects are one thing

3240.293 -> that access modifier could be used is

3242.8 -> to control the visibility of a particular class

3246.075 -> or a method as well.

3247.753 -> We have access modifier for your methods as well.

3252.1 -> So this is just one

3253.32 -> of the things right we would see other modifiers

3256.4 -> as well modifies in general has some other things as well.

3260.2 -> But when it comes to access modifiers it basically

3263.5 -> controls the visibility of a class visibility of a class

3267 -> or a method or so.

3268.7 -> Yeah modifiers here

3270.2 -> as you could see there is access and on access modifiers,

3274.611 -> let's see access modifiers.

3276.8 -> So we use public already.

3279.443 -> So this one is nothing but a access modifier

3282.8 -> which is public which says

3284.715 -> that it could be used throughout the application so

3288.4 -> visible to the world

3289.742 -> as it says public is nothing but visible to the world.

3293.3 -> If we talked about in a logical order

3295.556 -> if we talk about the visibility

3297.7 -> so default is visible to the package.

3300.8 -> So default is nothing

3302.245 -> but within the package it would be visible.

3305.186 -> So basically you could default

3307.274 -> is without any keyword without any access multi-faith.

3310.824 -> That's a default scope So

3312.53 -> within the package it would be accessible only

3315.6 -> within the package.

3316.9 -> So you have like calm down Eureka.

3319.3 -> That's your package.

3320.4 -> Right?

3320.9 -> So this hello world would be accessible

3323.8 -> if it has a default scope.

3325.8 -> It would be accessible only within calm down Ed Eureka.

3329.4 -> If you try to access it

3330.766 -> from some other package you would get an error.

3333.7 -> So that's the default visibility:visible to

3336.9 -> the package private is nothing but it is visible to the class.

3341.8 -> It is only visible to the class.

3343.9 -> So this is the lowest visibility only visible to the class.

3347.442 -> If you try to access it from outside class even

3350.245 -> within the same package you would get an error

3353.133 -> because You won't be able to access it is accessible only

3356.523 -> within the class public is accessible to the world.

3359.58 -> It could be accessed from anywhere within your application

3363.265 -> or anywhere within your wherever your class file.

3366.2 -> So basically if you if you have a jar file,

3369.1 -> but what I'm trying to say is public is accessible

3372.7 -> anywhere right protected is again visible to the package

3377.751 -> and all the sub classes.

3380 -> So we will talk about sub classes.

3382.4 -> So subclasses is nothing but in C we have inheritance,

3386.476 -> right say for example

3388.1 -> integer integer is a class

3390.6 -> as I said in object-oriented Paradigm or in Java everything

3394.871 -> could be visualized as a class.

3397.1 -> So integer itself is a class, right?

3400 -> So there's a number there is a super class

3402.916 -> which is number which has all the common state and behavior

3406.9 -> that a particular number would have right

3409.596 -> so number is a super class

3411.411 -> and you have subclasses

3413.067 -> like Teacher float would be a subclass

3415.686 -> of number long would be a subclass of number.

3418.8 -> Basically.

3419.523 -> This is inheritance,

3420.7 -> right you are inheriting integer float long double and everything

3426.5 -> from number class.

3427.9 -> So number is a super class and all this integer float

3432.3 -> and everything is a subclass of number.

3435.157 -> So when it comes to protect it,

3437.6 -> it says that it is visible to the package

3440.676 -> and of the sub classes,

3443 -> so just to keep in mind as of now,

3445.403 -> you can think of access modifier as visibility

3448.6 -> of a particular component

3450.325 -> or could be visibility of a class or visibility

3453.5 -> of a method or instance variable as well.

3456.6 -> This is what drives the encapsulation factor

3459.567 -> of object-oriented Paradigm.

3461.5 -> So basically we control the access or all this components

3465.607 -> or we control the access

3467.3 -> of class variables methods and everything

3470.1 -> which makes it encapsulated cannot be breached.

3473.6 -> Sort of as you could see this is

3476.6 -> like I could make this one as default as well.

3480.7 -> All right, so this is default scope.

3483.2 -> It would still run because it's within the class.

3488.4 -> Right now suppose I make this one as private, right?

3494.4 -> Just to show you what this encapsulation is all about

3497.7 -> or what this access modifier is all about suppose.

3500.9 -> I make this one private right still this one runs

3503.911 -> because it within the class you are trying to access it

3507.3 -> within the class now.

3509 -> I create a new class say for example,

3511.8 -> we say axis modified test.

3517.6 -> So I create a main class here again main method.

3522.9 -> Now suppose if I try to run this, right?

3525.727 -> So basically I create the same stuff here.

3528.7 -> See I create a hello world object.

3532.2 -> Okay.

3535.3 -> Now this one is private right now.

3537.483 -> If I try to access it from here,

3539.7 -> what I was trying to say is if I SEC

3545.769 -> as you could see here it says

3548 -> that nonstatictest has a private axis to hello world.

3552.2 -> So you cannot use it from outside.

3553.925 -> That's what I was trying to say.

3555.683 -> So basically since it has got a private scope

3558.1 -> you cannot access it from other class.

3560.3 -> And if I remove this private now with gives it default scope and

3564.202 -> as we said default is nothing

3566.06 -> but it has got access

3567.406 -> within package you could see this error going off here

3570.804 -> now it is accessible, right?

3573.1 -> So that's what is it is all

3574.9 -> about when you have a private scope.

3577.6 -> It's within a class.

3579.4 -> There is default is

3580.797 -> within a package public is accessible anywhere

3584.078 -> and protected is visible to the package

3586.849 -> and just the subclasses.

3589.611 -> So let's talk about non access modifiers.

3592.8 -> This is not controlling the axis of class method or variable

3597.2 -> when it static you did not create object of a class.

3600.9 -> So basically for static test you could see

3603.5 -> that we didn't create object of a class.

3605.9 -> We didn't call static test on a particular object of class.

3609.3 -> It could be called directly.

3610.966 -> That's what static is all about the static modifier

3614 -> for calling methods

3615.166 -> and variables without an object to which it belongs

3618.178 -> as we saw we didn't create object

3620.173 -> of our fellow world we directly cause the static method final is

3624.1 -> nothing but you can't change it final

3626.5 -> as the name suggests.

3627.9 -> You can't change it once it is created.

3630.135 -> So finalizing the implementations

3632.2 -> of classes methods

3633.6 -> and so this is nothing but instance variable

3636.304 -> which we would be talking

3637.783 -> about the slides to come just

3639.5 -> to tell you this is an instance variable

3641.8 -> which we have assigned the value 10 now suppose

3645.024 -> within this particular method I try to change the value to 11.

3649.3 -> You would get an error saying

3651.2 -> that cannot assign a value to final variable.

3654.098 -> So final is like its final can't change it

3656.9 -> once you have created it.

3658.2 -> You can't change it.

3659.2 -> But if I remove

3660.115 -> this final you could see this error would go off.

3663 -> You don't see this error anymore.

3664.895 -> Whereas by putting final you would see this error.

3667.877 -> So that's what final is all about.

3669.782 -> So basically this is good enough for constants, right?

3673.029 -> So if you have constants

3674.5 -> within your class you would make it final

3677.231 -> so that no one can change it abstract is nothing but

3680.591 -> you could mention it as abstract

3682.728 -> when it doesn't have implementation

3685 -> of all the methods.

3686.8 -> So what I am trying to say is abstract modifier is

3689.8 -> again a non access modifier and what it tries to say is say,

3693.817 -> for example,

3694.629 -> you have a shape class cheap class is abstract class

3698.389 -> because shape doesn't say you want to calculate

3701.6 -> area of shapes.

3703.1 -> So basically shape class

3704.885 -> by itself wouldn't know what the area of the ship would be.

3709.2 -> Is a class where in the generic class it doesn't know

3712.89 -> what the implementation of area would be 4 Square.

3716.271 -> It would be Side Square

3717.899 -> for rectangle its length into breadth or Circle.

3721.193 -> It's pie R square.

3722.515 -> So basically shaped by itself wouldn't know

3725.505 -> what it's area would be

3727.162 -> but now shape is a super class and say you have subclasses

3731.162 -> of it like Square you would have Circle and so on.

3734.616 -> So now basically you want to ensure

3736.909 -> that when you create a subclass

3739 -> of the shape class you want to ensure

3741.499 -> that that particular class implements the area that's

3744.812 -> when you create it as abstract.

3746.889 -> So the shape method would have

3748.9 -> of the shape class would have area method as abstract

3752.8 -> which would be implemented by the subclasses

3755.776 -> which has to be ensured its kind of ensuring

3758.803 -> or if the subclasses don't actually implement

3761.746 -> it you would get a error.

3763.477 -> So basically Circle would have its own implementation of areas

3767.696 -> in pie R square square.

3769.371 -> Would have its own implementation

3771.7 -> saying Side Square.

3773.105 -> So basically what I'm trying to say is area is abstract method

3777.458 -> for shape class.

3778.6 -> And when you have abstract method the class

3781.3 -> itself is abstract.

3782.624 -> So you have like shape calm down Eddie record dot shape.

3786.594 -> I'm creating a class now.

3788.377 -> I'm creating a abstract method So when you say abstract,

3792.3 -> you don't have to provide implementation.

3794.547 -> It's just a chain break this thing you don't have

3797.064 -> implementation of it.

3798.329 -> You just have the signature of it.

3800.394 -> So basically as I said,

3801.9 -> when you have an abstract method the class

3804.6 -> itself should be abstract.

3806.371 -> So we'll have to make this abstract as well.

3809.3 -> So you created a shape class

3811.06 -> which would have a area and which would give you this thing.

3814.682 -> So basically we want to have subclass and want to show

3817.918 -> how the sub classes are created at this point.

3820.504 -> But basically this is what abstract is all about.

3823.105 -> You don't have the implementation of it,

3825.4 -> but you are ensuring that subclass is implemented.

3828.226 -> So here you can see Just a signature.

3830.544 -> You don't have implementation

3832.1 -> unlike this implementation is nothing but

3834.452 -> if you write something within this braces,

3836.726 -> this is an implementation for this particular method,

3839.785 -> whereas in shape class.

3841.121 -> You just provided the method signature,

3843.394 -> but we don't have limitation of it.

3845.511 -> So that's what abstract is all about synchronized

3848.5 -> and volatile is much

3849.941 -> about using threads synchronized is we are saying

3853.5 -> that only one thread could get a control at one point.

3857.1 -> So as we said threads are nothing but parallel execution

3860.724 -> you could have thread say for example,

3863.16 -> you could have read one calling a method.

3865.901 -> So we have as non static method test

3868.271 -> right say this is a method.

3870.1 -> So what we are trying to say here is

3872.398 -> if it's synchronized we can make

3874.5 -> this a synchronized private synchronized.

3877.343 -> So this is what id is all about.

3879.545 -> So when you have this integrated development environment,

3883.4 -> you don't have to type everything

3885.464 -> when you type S why you could see synchronized coming up here.

3889.4 -> Put selected.

3890.3 -> So when you put a synchronized here,

3892.459 -> what we are trying to say is only one thread could access it

3896.4 -> at a given point only one thread at one point.

3899.8 -> So if multiple threads are trying to access it

3902.6 -> one thread has to wait for it.

3904.459 -> So only one thread would get entry to this

3907 -> and the other thread should wait for it.

3909.3 -> So that's what synchronized is all about and volatile.

3912.8 -> It's basically for memory visibility or

3915.6 -> what we are trying to say is so basically every processor

3919.9 -> has got its own cache.

3922.107 -> So what we are trying to say is

3924.6 -> when you use a volatile access specifier don't store it

3928.7 -> in Cash Store it directly into the main memory

3931.7 -> so that all the threats

3933.052 -> would get the most recent value being assigned

3935.9 -> to a variable also volatile is not needed

3938.6 -> when you have using synchronized

3940.5 -> as such so it's mutually exclusive.

3943.5 -> So let's talk about variable.

3945.415 -> So variables are nothing but it's a holder, right?

3949.2 -> Holds value and variables are nothing but it's reference

3952.937 -> to that particular meal

3954.6 -> or it's a dress or something

3957 -> that is pointing to a memory location a memory location

3960.2 -> where the squirrel use are being stored

3962.188 -> and you could access it using this particular variable name

3965.699 -> or you could access the memory location

3968 -> where the value is stored using a variable name

3970.8 -> what I'm trying to say here is

3973 -> so this is a variable and you could access

3976.4 -> so this 10 is stored somewhere in the memory

3979.148 -> and you could access this part of memory location

3982.215 -> where this 10 is stored using this variable

3984.9 -> or you can manipulate it as well can change the vat.

3988.7 -> So basically there are three types of variables in Java

3992 -> this local instance class or static local is nothing

3995.79 -> but local to your method whenever you have a method

3999.603 -> or you kind of create a variable within a method

4003 -> that is nothing but local scope which is

4005.555 -> like it has the axis its visibility only within that.

4009.18 -> Particular method once control goes out of this method you

4012.991 -> can no longer access is particular variable

4015.8 -> that is local.

4016.766 -> So if I Define something here say, for example,

4019.942 -> I Define something here.

4021.611 -> So this is a local variable

4023.8 -> since its defined within a method.

4026.2 -> So once the control you would have this only

4029.027 -> within this particular method,

4031 -> once the control goes out of this method.

4033 -> This is no longer accessible.

4034.727 -> Basically, this is

4035.8 -> where garbage collection for Java is useful.

4039.1 -> Once you control goes

4040.424 -> out of this particular method garbage collector would kick in

4044.302 -> and were dean of this variable

4046.005 -> or clean of this particular memory location or would make

4049.5 -> it available for use.

4051.3 -> So that's the local scope.

4053.012 -> The next one is

4053.994 -> instance instance is nothing but something

4056.73 -> that is defined at the instance level.

4059.2 -> So this is instance variable.

4061.3 -> So since it's at the class level,

4063.9 -> right this is you could see it at the mid-level.

4067.2 -> This is at the class level.

4069.1 -> This is nothing but an instance variable now there

4072.6 -> is static variable as well.

4075.3 -> So this is how you define a static variable.

4078.3 -> So instance variable is nothing but it's per instance

4082.6 -> so you could go and change this instance variable

4085.9 -> to something else suppose.

4087.9 -> I assign a value for T here now.

4090.4 -> I could have one more object created suppose I call

4094.246 -> this object one

4095.4 -> and I have Hello World object.

4097.919 -> So I create one more object here.

4100.4 -> So what we are trying to do is we are trying

4102.9 -> to change the instance variable through objects.

4106.3 -> So basically this is what it is when you

4109.2 -> have an instance variable normal instance variable,

4112 -> which is non static you could access it

4114.7 -> through objects, right?

4116.278 -> So throughout object one you

4118.208 -> assign for object one you assign instance variable value

4122 -> to 44 object to rinse you change the instance

4126.1 -> variable value to 50.

4128 -> I won't say Changed it.

4129.711 -> But you assigned it.

4131.2 -> This is how you deal with instance variable.

4134 -> It's at the instance level.

4135.869 -> It's at the object level.

4137.6 -> Whereas for static.

4138.979 -> It's at the class level.

4140.7 -> It's one per class.

4142.035 -> It's not one per instance.

4143.864 -> It's one per class.

4145.193 -> So basically what you can do is you could do something

4148.9 -> of this sort where in its at the class level.

4151.552 -> It's not at the object level.

4153.3 -> You are assigning value hundred to a static variable.

4156.4 -> So as you could see here,

4158.2 -> it's not a particular instance

4160 -> that you're operating on its the class directly

4163 -> just to give you a just we have local variable

4165.73 -> which is within a particular method and scope

4168.4 -> remains within a method.

4169.9 -> Once the program control moves

4171.999 -> out of this particular method Java would or jvm would come in

4176.131 -> and kick in garbage collector to clean this off Sony accessible

4180.5 -> within this menu you have instance variable,

4183.2 -> which is at the class level,

4185.384 -> but it's non-static and which means

4188 -> that it has copy.

4189 -> Per object when you have multiple objects,

4191.9 -> you could change the values the way you want

4195 -> per object static is nothing

4197.1 -> but 1 per class and as you could see here,

4200.4 -> we change the value of the static variable 202 class.

4204.4 -> So that's about variables.

4206.5 -> We have an instance.

4208.4 -> So instance variables are declared in a class

4210.722 -> when the space is allocated.

4212.213 -> I will just read through this one.

4214.1 -> So when a space is allocated for an object in the Heap slot

4217.6 -> for each instance variable is values created.

4220.497 -> We had a your instance variable

4222.46 -> and whenever you create but basically an instance

4225.8 -> of a class is created in a part of a memory,

4228.5 -> which is called Heap.

4230 -> So whenever hello world object is created a slot

4233.6 -> for this instance variable

4235.4 -> would be treated as well instance variables are created

4238.9 -> when an object is created

4240.554 -> with the use of keyword new and destroyed

4243.2 -> when the object is destroyed.

4245.1 -> So unlike local variables,

4246.848 -> which is within the method scope.

4249.2 -> Variable is within the class scope.

4251.2 -> So basically whenever you create an instance

4253.742 -> of a particular class,

4255 -> your memory would be allocated

4256.723 -> for that particular instance variable.

4258.9 -> And whenever it's done

4260.2 -> whenever it's destroyed by the garbage collector,

4262.9 -> it would go off

4263.98 -> access modifiers can be given two instance variables.

4267.7 -> You could have like private public protected default

4271.2 -> all the access modifiers.

4272.8 -> We assign to students variable.

4274.731 -> So basically you could have it

4276.6 -> as private private is just within this class.

4279.8 -> You cannot access it

4280.8 -> outside this class you could have public as well,

4283.74 -> which is like would be accessed anywhere within this application

4287.6 -> you could have protected

4289.24 -> which is like within the package

4291.465 -> or the subclass and you can have the default one which is nothing

4295.759 -> but package axis,

4296.9 -> which would be accessible just within this package

4299.9 -> that is calm dotted Eureka.

4301.6 -> So instance variable have default values

4304.2 -> for numbers the default value zero for Boolean it

4307.4 -> is false for all.

4308.9 -> Big references it is null

4310.823 -> so values can be assigned during the Declaration

4314.7 -> or within the Constructor you could assign values directly

4319.1 -> while declaring it something

4321.1 -> like this instead of 0 is the default one for integer

4324.8 -> as they have mentioned.

4326.07 -> But yeah, you could assign

4327.6 -> if you put it as 10

4328.9 -> here it would be taken as a default value

4331.5 -> zero zero Constructor is nothing but a method

4334.5 -> which constricts an object

4336.5 -> of a class values can be assigned during the Declaration

4340.2 -> or within the Constructor instance variables

4343.368 -> can be accessed directly by calling the variable name

4347.2 -> inside the class.

4348.2 -> However, with static methods

4350.8 -> when instance variables are given access ability.

4353.913 -> They should be using fully qualified name.

4356.571 -> So what we are trying to say here is this is a static method

4360.287 -> from which we are trying to access instance variable

4363.6 -> in this particular static method you need

4366.2 -> to have object reference.

4368.2 -> This is Object that we created so

4370.8 -> object reference dot instance variable you need to have

4374.175 -> as we have mentioned here.

4375.8 -> So here as we can see object reference

4378.147 -> to a variable name.

4379.352 -> You need to have fully qualified name.

4381.7 -> When you try to access it within the static method.

4384.2 -> You need to have fully qualified name.

4386.1 -> Whereas here within a method which is non static.

4389.8 -> This is non-static here.

4391.501 -> I can access instance variable without object reference.

4395.5 -> So here as we can see it could be accessed without but

4399.5 -> if I do it here it would throw me an error.

4402.508 -> It's not accessible here at all.

4404.8 -> Non-static Fields instance variable cannot be referenced

4408.351 -> from static context instance variables are

4411.3 -> not accessible directly here.

4413.6 -> It has to have fully qualified this thing,

4416.1 -> which is object reference dot instance variable.

4418.9 -> Whereas when it's called

4420.6 -> within non static method you could use the direct so static

4424.919 -> as we spoke about it's one per class,

4427.6 -> so it's declared.

4428.9 -> Using static keyword.

4430.4 -> So static variables are stored in static memory.

4433.3 -> It is rare to use static variables other

4435.6 -> than declared final

4437.061 -> and used as either public or private constants as we said,

4442.3 -> it's mostly used for constants and static variables are created

4447.215 -> when program starts

4448.6 -> and destroyed when the program stops.

4451.054 -> So one thing to remember is it's one per class.

4454.1 -> It's not one per object instance is one per object.

4457.4 -> We have a copy of that particular instance variable one

4460.7 -> per object case of instance,

4462.887 -> whereas case of static it is one per class.

4466.5 -> So the scope remains are the life cycle remains right

4470.052 -> when the class is loaded in the program is stopped

4473.4 -> in the class is unloaded static variables are declared public

4477.6 -> since they must be available for users of the class.

4480.7 -> It's not mandatory though,

4482.5 -> but usually if it's a constant it is declared

4486 -> as public static variables can be accessed by A calling

4490 -> with the class name.

4491.207 -> So we saw here last name dot static variable.

4494.6 -> So how do we decide what amount of memory is to be allocated?

4498.502 -> So these are the data types that we have.

4501.1 -> So each variable in Java has a specific type

4503.804 -> which determines the size of memory the range of values

4507.2 -> that can be stored and the set of operations

4509.974 -> that can be applied

4511.2 -> to the variable data types can be categorized

4514.26 -> into two major types primitive and non primitive.

4517.633 -> So basically primitive is not object primitive

4521.134 -> is supported by language itself,

4523.6 -> which is kind of it has got 8 primitive

4526.222 -> or its pre defined by the language

4528.5 -> and named as keywords and it has 8 primitive data types

4532.5 -> that is byte short integer.

4534.6 -> Then you have long float double character and Boolean.

4538.6 -> This is pretty much similar to other programming languages

4541.7 -> that you have by it consumes one one bite.

4544.8 -> These are 8 primitive data type set of predefined non-primitive.

4549.1 -> It's nothing but string string is object itself.

4552.806 -> So that's something

4554.3 -> that is non pyramid or if we Define

4556.593 -> your own class C student for that matter here, right?

4560.1 -> We have defined student class that's non primitive.

4563.1 -> So this student class has non primitive you have strings

4566.667 -> for storing string,

4567.922 -> which is again kind of non primitive.

4570.3 -> We have arrays

4571.91 -> or basically it's all as reference variables

4575.3 -> since referencing a particular memory location

4578.322 -> through variable name.

4579.798 -> This is where we have table showing white consumes one bite

4583.831 -> and it's range is from -

4585.5 -> 128127 short is like two bites and you could imagine

4590.2 -> that it would be from - 32768232767.

4594.9 -> So it's pretty much similar to other programming languages

4597.991 -> that you have like in C as well we have similar to this thing.

4601.3 -> One thing is characteristics to bite in C takes one bite.

4604.752 -> I believe though.

4605.8 -> It doesn't use all the two bites every time it.

4609 -> On encoding type.

4610.6 -> So Boolean is one which is true of all

4613.234 -> since it has to store 1 or 0.

4615.3 -> So it's pretty much similar.

4616.7 -> So just to talk on the bytes required by test 1 byte short is

4621.3 -> 2 bytes integer is 4 bytes long is 8 bytes float is nothing

4626.282 -> but it has decimal values stored signed decimal values.

4630.6 -> So it again concerns

4632.4 -> for bites double is sign again float values

4636.5 -> or sign decimal values

4638.8 -> which consumes 8 bytes character is 2 bytes

4642.576 -> and bullion is one bit.

4644.6 -> So basically so decide

4646.3 -> whether to use float or double depends on the nature

4649.5 -> of the application.

4650.697 -> So if you want to have more Precision or

4653.172 -> if you want to have more range you could go with double so non

4657.159 -> primitive or reference data type is a variable

4660.2 -> that holds a particular object or holds bit

4663.2 -> that represents a way to access an object the pointer

4666.767 -> to a memory location baisakhi.

4668.8 -> So as we spoke Java doesn't expose the pointer directly.

4672.4 -> It doesn't give you directly pointed to the memory location,

4675.705 -> but it gives you the reference variable.

4678 -> So you cannot manipulate memory location directly.

4681.5 -> You cannot add some values

4683.4 -> to the memory location through pointers or something

4686.106 -> but through reference variable you can access it

4688.6 -> and assign someone so

4690.112 -> yeah, it does not hold the object itself,

4693 -> but it holds a reference address

4695.461 -> to the object reference type does not have size or bit range.

4700.6 -> So here we can see string Str is equal to Ed Eureka.

4705.3 -> So the one shown

4706.6 -> in red is actually the memory we're dead Eureka is stored.

4710.714 -> You have a reference and Str is the reference to it.

4714.796 -> So here we can see variables and data types.

4718 -> So we have a main method again and we have bite.

4722.1 -> We declare a bite here by D is equal

4724.6 -> to 10 short s is equal to 20,

4727.1 -> so, I think it's pretty straightforward.

4729.2 -> You kind of have this data types created you just have

4732.826 -> to assign values to it.

4734.4 -> These are all Primitives as you could see till here.

4737.5 -> It's primitive so you could see that values are being assigned

4741.4 -> and it's been printed out here.

4743.5 -> So I think it's pretty straightforward.

4745.5 -> You can assign a value to a variable n just print.

4748.1 -> So again, we use system dot out dot println

4751.4 -> for printing it you could try it out on your own.

4754.8 -> You could try it out this data type program.

4757.9 -> You could just assign something and just try to print it out.

4761.5 -> We are talking about data type conversions.

4764.5 -> So we have implicit

4766.076 -> and explicit conversion

4768.1 -> in some case programmers don't have to actually

4771.1 -> write explicit conversions from one data type to other

4774.3 -> but in many cases programmers need

4777.1 -> so the arrow in the diagram

4778.8 -> shows the possible implicit type casting

4781.8 -> that a permissible bit primitive data types.

4785.1 -> It's just with primitive data types right as the diagrams.

4789 -> Those int can be converted implicitly to Long float double

4794.7 -> since int X likes less space.

4797.925 -> It could be applied to any of the numbers for vice versa.

4802.232 -> They have to be converted explicitly.

4805 -> Whereas if you want to convert long to integer,

4808.3 -> you have to mention it explicitly.

4811.1 -> So basically we are talking about when you're trying

4814.4 -> to store integer into long integer takes less space

4817.701 -> and long takes more space.

4819.366 -> So it should can be easily accommodated

4821.8 -> since long takes more space.

4823.8 -> If it is more than the range of the integer.

4826.5 -> It wouldn't know how to assign it to an integer.

4829.4 -> So that's why it has to be explicitly

4832 -> convert implicit conversions.

4834.3 -> We can on the J shell you could type this.

4837.8 -> So here what we are trying is we have a character C is equal to a

4842.884 -> and you could see see

4844.5 -> is assigned a now integer K is equal

4847.7 -> to C. Which could be done you could assign character

4852.411 -> to an integer.

4853.8 -> So basically it's a ASCII code for it.

4857.5 -> So 97 is the ASCII code for see which would be assigned to K.

4862.2 -> So now when you assign see to float,

4865.587 -> which works as well,

4867.3 -> so you get ninety seven point zero you could assign

4871.2 -> character to long as well,

4873.25 -> which is in bytes integer,

4875.657 -> you could assign double as well,

4878.2 -> which is 8 bytes float and you could see

4881.1 -> but it cannot be done the other way around

4883.4 -> as we spoke.

4884.4 -> So you cannot have integer

4886.661 -> or you cannot have double assigned to character.

4890.7 -> So it would give you incompatible

4893.1 -> our possible lossy conversion from double to character.

4897.2 -> It has to be explicitly done.

4899.2 -> If you want to do that need of type conversions.

4902.8 -> So here we have integer a full 200 initiated a variable

4907.9 -> with type Teacher then you have a string B,

4911.526 -> which is assigned value.

4913.399 -> Hello.

4914.2 -> So basically here you can see string being used

4917.572 -> which is a reference variable and you have string s is equal

4922.6 -> to a plus b as equal to a plus b then it adds up like hundred

4928 -> plus since hello is a string it would concatenated

4932.9 -> so you could see hundred

4934.312 -> and hello being concatenated and you could see hundred.

4937.5 -> Hello the data type of both the variables are different

4940.957 -> but to perform any operation we need both the variables to be

4944.8 -> of same type here integer value is converted into string

4948.544 -> and gets concatenated with other string.

4951.3 -> So basically had we been an integer you

4954.338 -> would have got edition of it say

4956.8 -> for example integer B is equal to 200 and if you hundred

4961.3 -> plus 200 you would get 300 but

4963.7 -> since it's a string in this case hundred is converted into string

4967.5 -> and it is concatenated.

4968.9 -> Hello explicit type conversions.

4972 -> We saw the previous case

4973.8 -> where an double was being assigned to character

4976.884 -> which prompted us with lossy conversion.

4979.5 -> So this is similar to that.

4981.481 -> So basically here

4982.78 -> what we are trying to do is we are trying to assign

4986.6 -> double to integer.

4988 -> So you have double D is equal to 45 B,

4991.9 -> which is 45 right again double is 8 bytes decimal

4996.2 -> signed decimal number

4998.8 -> so you assign 45 to it.

5001.1 -> And now we are trying to assign this double value to integer.

5005.7 -> So it's possible lossy conversion,

5008.8 -> but you have a provision to type Custer.

5011.81 -> So basically what we're trying to do here is you're trying

5016.2 -> to assign again double to integer which is possible

5019.862 -> if you type casted so

5021.4 -> when I say typecasting it's nothing but opening parenthesis,

5025.3 -> then the destination data type then your data.

5028.761 -> To a table.

5029.7 -> So basically to the right side you could see

5032.4 -> that through explicit type casting we can assign

5036.071 -> double to integer.

5037.738 -> So costing may lose information.

5040.2 -> For example, floating Point values are truncated

5043.3 -> when they are cast two integers example the value of D.

5047.8 -> That is 45.5 when converted to integer gives 45

5053.03 -> so we could see here the bottom like the double

5056.838 -> we assigned the value of 45.5 to double

5059.9 -> but when we convert it into integer,

5062.5 -> we got 45.5 Force truncated since double since integer

5067.9 -> since the destination data type

5070.2 -> that's integer dozens to decimal values.

5073.5 -> Now, this is like type conversion methods

5076.8 -> which is there any wrapper classes?

5080 -> What we are trying to do here is we are trying to convert 23,

5084.789 -> which is string into integer.

5087.4 -> So you have a string.

5089 -> As is equal to 23 you assign the value 23 so mind

5094.1 -> you this is this is string right now.

5096.5 -> We have integer dot parse int and we pass the string

5100.6 -> which would be converted into integer.

5103 -> So this integer class

5104.7 -> that you see here right here is nothing

5107.623 -> but butter wrapper class you have string into an integer,

5112.7 -> which is nothing but integer dot value of string

5115.9 -> which converts it into digital data type itself.

5120.2 -> So the you could see the destination is is integer.

5124.4 -> Now integer to string you have integer.

5127.556 -> We have a tostring method

5129.37 -> which with converts integer into string.

5132.3 -> So basically you have integer I which is been assigned 23.

5136.684 -> Now you have integer dot tostring I

5139.515 -> which would convert this integer into string.

5142.9 -> We have one more method

5144.577 -> which is string dot value of which would also convert.

5148.586 -> Integer into string.

5150.1 -> Let's talk about operators operators are

5153.446 -> nothing but it operate on this data types.

5156.6 -> So you have unary

5158.1 -> which is kind of pretty much similar to what you

5161.6 -> have C C++ you have post fix and you have prefix post fixes.

5167.4 -> I plus plus or expression

5169.4 -> plus plus and the operator is after the variable which means

5173.792 -> that it would be assigned value

5176.1 -> and then it would be added prefix is before the operator

5180.4 -> which would be added first

5181.65 -> and then assign or the operation would be done first

5184.4 -> and then assign that's prefix arithmetic is

5187.657 -> pretty much similar like multiplicative you have

5191.3 -> like multiplication division and mod you have additive which is

5196.2 -> plus and minus you have shifting operation,

5199.03 -> which is bits shifting to the left and bit shifting

5202.4 -> to the right you have relational operators less

5205.9 -> than greater than less than equal to greater

5208.1 -> than equal to.

5209 -> Instance of Quality quality of two data types

5213.4 -> or two variables which check

5215.5 -> whether they are equal and not equal.

5217.9 -> We have a bitwise

5220 -> and bitwise xor bit wise inclusive or

5224.2 -> which is happening at the bit level.

5226.7 -> We have logical and logical or so.

5229.9 -> Basically, this is for conditions, right?

5232.583 -> If you want to have like two conditions,

5235.2 -> like if int I is greater than 0

5238.4 -> and int J is greater than zero sort of you add

5242.1 -> or you have logical anding

5243.912 -> between two conditions logical conditions

5246.9 -> or illogical or pretty much similar

5249.515 -> to other programming languages.

5251.899 -> Like it's or between two conditions.

5254.5 -> We say that either this or that we have a ternary operator,

5258.7 -> which says that

5259.727 -> if the condition matches we would have a condition followed

5263.7 -> by a question mark followed by colon,

5266.1 -> and we would have some value

5268.5 -> Followed by colon followed by some other value.

5272 -> So what we are trying to say here is

5274.4 -> if the condition is true assign value 1

5277.1 -> if the condition is false then assign value to so

5280.3 -> instead of having it written in

5282.4 -> if else you try to put it within turn your printer.

5286.9 -> So basically this is when you have simple assignment operator,

5290.788 -> if you have a logic

5292 -> if you have some particular logic been written it would be

5295.229 -> a better practice to have

5296.7 -> if else so that it's readable right

5298.705 -> because ternary operator

5300.198 -> it would be very difficult to actually

5302.5 -> through we have assignment operator

5304.807 -> which is equal to which is plus equal to is nothing

5308.2 -> but adds the value on the right hand side

5310.759 -> to the left hand side and assigns it

5313.1 -> to the left hand side table -

5315.25 -> equal to does the same thing.

5317.4 -> It kind of subtracts value

5319.4 -> to the the left hand side from the value to the right hand side

5323.448 -> and assigns it to the left hand side.

5325.8 -> So I believe this is pretty much similar to other programming.

5328.8 -> Languages there's nothing

5330.1 -> different in this we might have used it somewhere

5333.487 -> or the else should be pretty much simpler for you guys.

5337.5 -> So let's see unary operator example

5340.8 -> when X is equal to 10,

5343.1 -> so you could see X been assigned value 10,

5345.9 -> you have X plus plus

5348 -> as we said it assigns first and then increments it

5351.8 -> so you could see value 10 here again.

5355.2 -> So now if you after this if you print the value of x,

5359.5 -> you should see the incremented value.

5362 -> That's 11.

5362.8 -> So that's post-increment.

5364.686 -> So, let's see pre-decrement.

5366.8 -> So you have a been assigned the value of 10.

5370.7 -> All right.

5371.5 -> Now, you do - -

5373.2 -> A which is pre-decrement you would see the value 9 directly.

5377.3 -> And now if you print the value of a it would be nine again.

5380.953 -> So basically this is

5382.167 -> like decrement and then assign this is like a sign

5385.542 -> and then operate this is like operate and then assign

5388.7 -> Let's see the negation operation like a has a value of true now,

5393.301 -> we negate it and assign it

5395.207 -> to the variable D and you could see

5397.7 -> that it's changed to false.

5400.1 -> Now.

5400.4 -> Let's see the arithmetic operator.

5402.7 -> You have B which has value of 20.

5405.238 -> We have D which has value of 30.

5408 -> So when you add it gives you value of 50

5411.2 -> when you multiply it gives you the value of 613 220

5415.3 -> which is 600

5416.5 -> when you divide it 30 by 20 you get value 1 and

5421.2 -> when you have mod,

5422.953 -> which is like remainder,

5424.8 -> which gives you value 30 by 20,

5427.107 -> which is equal to 10 shift operators are

5431 -> so it shifts to the left so shift left shift, right?

5435.3 -> So basically you have integer value of 20 and

5439.1 -> if you convert this into binary

5441 -> if you convert the 22 binary

5443 -> which comes out five digits, right?

5445.6 -> So when you convert this binary and when you shift,

5448.7 -> To the left you would get the value of 80.

5451.4 -> So you have value 20,

5453 -> which is nothing but if you convert this 20 into binary,

5457 -> which would give you one zero one zero zero right.

5462.5 -> Now, what we're doing here is kind of Shifting it

5466.3 -> to the left by 2.

5468.026 -> This is what you do and this is what it shows up as value of DT.

5473.1 -> So this is nothing but 64 plus 16.

5476.853 -> So that's what this left shift does.

5479.7 -> Basically it shifting to the left by 2.

5482.6 -> Again, you could have shifting to the right by 2 by 3,

5486.6 -> which would give the value of to just shifting

5489.469 -> to the right by 3 would be something like this.

5492.6 -> Right?

5493.022 -> So you're basically it shifts it and you could see that.

5497 -> Yeah, basically it would end up to 2.

5499.8 -> So now we have like relational operators,

5502.776 -> which is pretty much simple like a less than b.

5506.6 -> It gives false a greater than b equals equals P.

5511.9 -> Since you have a is equal to B.

5514.8 -> In this case.

5515.564 -> We have a equal to B.

5516.726 -> That's why we have a less than b as false

5519.079 -> and a greater than b as false.

5520.8 -> But whereas a equal to equal to B is equal to 2,

5524 -> we have arithmetic operators pretty much similar.

5527.1 -> Basically you have ad you have

5529.139 -> multiplication you have division you have mod.

5532.4 -> So here we have a is equal to 20.

5535.9 -> So what we are trying to do is assignment so a is equal

5540.053 -> to 20 now B is equal to 40 a plus equal to B,

5543.6 -> which is nothing

5544.624 -> but as I said,

5545.483 -> your left hand side would be added up to the right hand side

5549.1 -> and would be assigned to the left hand side,

5551.5 -> which is nothing but 20 plus 40 would be assigned to a so

5555.8 -> when you print a it would print 60 ternary operator,

5559.5 -> which is nothing but if a is less than b here we can see

5563.344 -> that if a is less than b then the value

5566 -> of Should be assigned to tr or the value 200 in this case.

5570.472 -> The value 200 is been assigned is greater

5573.4 -> than b logical operators is nothing but anding

5577.1 -> and o-ring of conditions.

5578.9 -> Yeah, here we are saying

5580.4 -> that a is less than B

5581.8 -> and D is less than b then return false

5585.1 -> and it's like kind of ending logical conditions.

5589.6 -> Now, let's talk about the control statement in Java.

5592.7 -> Now again, this one is pretty much similar

5595.3 -> to other programming languages

5597.493 -> nothing different nothing different in Java.

5600.576 -> So you have control statements you have I treat

5604.175 -> if statements you have jump statements.

5606.9 -> So one is selection or decision making statements,

5610.377 -> which is like if else if else ladder you have

5613.504 -> if if this particular condition satisfies do some things do

5617.502 -> some execute group of statements

5619.708 -> and if it doesn't then execute other group of statements

5623.5 -> that is about

5624.5 -> if else Which is nothing but based on the value of a variable

5629.7 -> like you to execute different step of statements

5633.484 -> like say for example,

5635.1 -> you have you write a switch

5637.9 -> on Integer value integer variable X.

5641.8 -> Now when X is 1 you do something or if x is 0

5647.1 -> you do something or you can have a default statement as well

5650.9 -> when X is either 0 or 1 do something else

5654.5 -> that supports which I tradition

5656.674 -> is you repeat the same set of statements again,

5659.9 -> and again till the condition

5661.731 -> till a particular condition is met that's a titration.

5665.131 -> So you have four Loops,

5666.608 -> which is like after every iteration the value of variable

5670.203 -> or the iterating variables would be changed

5673.091 -> and would be checked against a condition and

5675.963 -> if it meets it would come out

5677.9 -> or if it made it would execute it again,

5680.6 -> and if it doesn't mean then it would come out.

5683.5 -> So yeah, this is pretty much similar to other.

5685.952 -> Other programming languages.

5687.6 -> So for for INT I is equal to Z 0 is less than 10.

5691.8 -> I plus plus

5692.7 -> and you write something within it.

5695.048 -> So this Loop would go on for 10 times from 029.

5698.317 -> It would break it would come out

5700.517 -> when eyes greater than 9 which is 10 when it goes to 10.

5704.3 -> It would come out

5705.307 -> while is again pretty much similar to that.

5707.8 -> You have do while construct

5710.1 -> which is guaranteed to be executed once

5712.488 -> because the condition is checked

5714.5 -> after the execution is done once

5717.4 -> so basically no matter what the condition is.

5720.7 -> It has to be executed once for sure.

5723.5 -> That's when if that's the behavior you want to put

5726.685 -> into your program you would use

5728.7 -> to Y is equal to once

5730.4 -> for sure jump statements you have like break

5734.7 -> which come out of for Loop Komodo for Loop

5738.3 -> or any attractive statements you have continued

5742 -> which would again continue and return is again coming out.

5746.215 -> Of a method or are mostly

5748.064 -> from the methods you written something

5750.8 -> so the control leaves the method now just to give you

5754.645 -> what if Wells is if if the condition is true,

5757.849 -> then then execute the conditional code.

5760.653 -> If the condition is false come

5762.797 -> out of the execution or come out of the conditional code.

5766.8 -> Skip the conditional code.

5768.5 -> That's what if else is so here you have int

5772.4 -> I is equal to 10 and int b equal to 20

5775.6 -> if I is less than b

5777.4 -> so it's pretty much similar to the ternary operator that we had

5781.4 -> so you could see here

5783.3 -> TR is equal to a plus b so basically the value

5787.674 -> if a is less than b which is in this case

5790.853 -> a is equal to 10 and B is equal to 20 in that case.

5794.7 -> You would have PR as 30 since it is true.

5799.3 -> So basically it checks the condition and

5801.7 -> if the condition is true it executes the code with now

5805.3 -> let's talk about If else if it

5808.1 -> if else construct is nothing

5810 -> but you have a is a set of statements to be executed

5813.5 -> when the condition is in satisfy succeed.

5816.5 -> So in this case

5818.1 -> if a is less than b TR is equal to a plus b else TR is equal

5823.5 -> to B minus a so in this case it was less than a

5827.9 -> is less than b so you got the value of 30

5831.9 -> whereas if a is greater than b we have again changed it.

5836.3 -> So if a is greater than b then TR is equal

5839.5 -> to a plus b else TR is equal to B minus a so

5844.3 -> in this case a is less than b so

5847.6 -> which means CR should be B minus a

5850.996 -> which goes into the else condition statement

5854.4 -> and here you have 20 be as 20 and a as 10

5857.9 -> which is 20 minus 10.

5859.515 -> So you should have PR as 10.

5862.3 -> So here it's pretty much same.

5866.3 -> It does the same thing nested if-else now,

5869.5 -> we are talking about the switch statement.

5872.585 -> So you have switch expression and you would have case written

5877.2 -> against it whatever case you want to execute.

5880.6 -> So basically you would have for Value 1.

5884.9 -> So yeah,

5885.4 -> what we are trying to say here is we have a switch expression

5888.3 -> and we have a value

5890.3 -> for Value 1 as its value then execute this piece of code

5895.015 -> and then break out

5896.4 -> and if it has value to then execute this piece of code

5899.9 -> and then break it doesn't match

5901.9 -> with value 1 and value to then executes the default cases.

5906.2 -> So one thing to note here is it's mutually exclusive only one

5910.579 -> of it would be executed out of the cases.

5913.5 -> Make sure you break

5914.961 -> out of all the the conditions so to the right hand side

5919.2 -> you could see integer CH has a value of 40 now.

5923 -> We have a switch for 40 now.

5926.1 -> Is when the value of CH is 20 it would print

5929.5 -> case 20 executor

5930.8 -> when its value is 30 then we would have case 30 executed

5935.1 -> when its value is 40

5936.521 -> then we would have case 40 executed

5938.873 -> and then break out and

5940.452 -> if it's neither 20 30 or 40 we would have a default case

5944.4 -> is executed with says

5946.108 -> that 20 30 40 not executed.

5949.2 -> So in this case

5950.6 -> since it has a value of 40 you would see

5953.5 -> that case 40 executed as output I'd frisson is nothing

5957.9 -> but it is basically I treating code

5960.34 -> if a condition is met the the code would be executed

5964.2 -> until the condition is true.

5966.4 -> The code would be executed and once once it is false,

5969.634 -> it would come out of the loop.

5971.5 -> So basically it's a looping statement.

5974 -> So after every Loop the condition would be checked

5976.576 -> and if the condition is true it would loop again.

5979.4 -> And if not, then it would come out.

5981.7 -> There are three types of for Loop in Java

5984 -> simple for Loop similar.

5986.1 -> See like for INT I is equal to 0

5989.5 -> I is less than 10.

5990.884 -> I plus plus would be a simple for Loop for each

5994.5 -> or an enhanced for Loop and labeled for Loop for each is

5999.914 -> basically I treating

6001.453 -> on array list suppose you have some collection

6004.951 -> or suppose you have a re right?

6007.6 -> You don't have to manipulate the indexes

6010.7 -> since the typical scenario

6012.7 -> with arraylist is I treating through all the elements

6016.218 -> within the list.

6017.341 -> So we have an enhanced

6018.886 -> for Loop wherein we don't have to actually deal with indexes.

6023.1 -> Java has come up with a enhanced for Loop

6026 -> where and what each iteration it would assign the value

6029.2 -> of each element within the array to a variable

6032.4 -> which could be used within the loop.

6034.568 -> So we don't have to deal with indexes

6036.8 -> like we don't have to Loop through

6039.355 -> till the sizes met in the loop

6041.7 -> through in the size of an array is Matt,

6044.7 -> basically it Done by Java itself.

6047.7 -> We have an example which would clarify it.

6050.792 -> So simple for Loop is

6052.6 -> as I mentioned you have for INT I is equal

6056 -> to 10 is greater than 1 I

6058.2 -> minus minus so it would print from 10 to 2.

6062.1 -> That's a simple for Loop.

6063.8 -> Now.

6064 -> What's the Syntax for it is for then open up round brackets.

6069.289 -> Then you have initialization.

6071.6 -> Then you have a condition and you have increment

6074.408 -> or decrement whatever you want to do

6076.6 -> or you could even add up like I

6078.695 -> plus equal to 2 even that is good enough.

6081.4 -> It's like for each even number not even I would say it's

6085.919 -> like incrementing by 2.

6087.5 -> Now.

6087.766 -> This is what I was talking about.

6089.9 -> So this is for each Loop or enhanced for loop.

6093.3 -> We're in a typical scenario with array.

6095.8 -> You kind of eye to it through each element

6098.2 -> within the array

6099.4 -> and then do something within the loop, right?

6102.6 -> So this is what Java has made it easier for us.

6106.2 -> So basically you don't have to deal with indexes here

6109.939 -> if we wouldn't have had for each Loop.

6112.6 -> What you would do is you would tell the size

6114.982 -> of the array is Matthew would I trade through and read

6118.1 -> from each indexes right?

6119.7 -> But in this case

6120.93 -> as you could see there's an array

6123.6 -> and for each Loop the value

6125.6 -> within the array would be assigned to this variable

6128.316 -> and you could use this variable

6130 -> within makes it pretty much simpler for us.

6133.2 -> And as I said,

6134.3 -> this is typical thing

6135.915 -> that we do with arrays

6137.9 -> now labeled for loop it's not recommended to use this often

6142.426 -> but still we have this construct here.

6145.7 -> So basically it's like go to we can have a label

6149.8 -> of each for Loop.

6151.2 -> It is useful we have nested for Loop

6153.892 -> so that we can break or continue a specific

6157.123 -> for Loop normally break

6158.9 -> and continue keywords continues the innermost Loop innermost

6163.6 -> for the loop only to give Behind why I mentioned

6167 -> that this should be used often is

6169.026 -> because it becomes very difficult to debug right?

6171.957 -> If you dry run it if you use this labels,

6174.6 -> it becomes very difficult to actually understand

6177.1 -> what's happening within so so we should avoid it

6180.5 -> and all this could be done by writing a proper construct.

6184.746 -> Sorry using simple for loop as well.

6187.4 -> So we should avoid it somehow so basically

6190.235 -> as per my experience is not a good practice to use them.

6194.02 -> So type of while loop we

6195.601 -> have SIMPLE while loop we have do-while Loop.

6198.5 -> All right.

6199.088 -> So simple wire Loop is first the condition is checked

6202.3 -> if it meets then the looping statements are executed

6205.479 -> whereas do-while Loop is kind of the statement is executed once

6209.3 -> for sure and then the condition is checked

6211.855 -> if it is met then it is looped again.

6214.1 -> If not, then comes out.

6215.619 -> So this is a simple while loop

6217.6 -> so you have conditioned as you could see here

6220.714 -> while a is greater than 1

6222.2 -> you print the value of a and you increase

6224.8 -> decremented Within Here it's a do while loop

6228.5 -> so no matter what you would have this to printer

6232.6 -> and it would be incremented.

6234.6 -> So it's 2 to 9.

6236 -> So no matter what some value would be printed for sure

6239.881 -> when you use do I now we have jump statements,

6243.126 -> which is breaking slyke coming out of a loop.

6246.3 -> So as we mentioned it's the innermost Loop

6248.826 -> that it comes out of so that's what Brave does

6252 -> if a particular thing is met or you could write a condition

6255.411 -> for a particular Loop to be broken rather

6257.9 -> than continuing it.

6259.2 -> So basically you could have like this would be more or less

6263.329 -> like you could have infinite

6265.239 -> Loop say for example running through and

6268.1 -> if a particular condition is met you could break out

6271.2 -> of it a typical scenario

6272.731 -> where it would be used.

6274.2 -> So here you could see that you have a loop from 10,

6277.968 -> which I traits from

6279.394 -> where I is equal to 10 and where I is greater than V i- -

6283.6 -> which we are decrementing each Loop.

6286.1 -> Whereas you're saying

6287.394 -> that if I is equal to equal to 7 we should break out.

6290.6 -> So here you can see though eyes

6293.2 -> greater than 5 you can see the loop has broken out after 8:00

6298.2 -> since the value has reached seven.

6300.5 -> It's not printing the other indexes

6303 -> because it broke out of the loop.

6304.882 -> So basically this is like

6306.4 -> if a particular condition is met

6308.4 -> and you don't want the loop to go ahead you can break

6311.7 -> out of the loop continue is similar

6314.462 -> when you write continue,

6316.2 -> it goes to start of the loop again,

6318.2 -> it starts the loop again

6319.8 -> and it skips the messages or it skips the code

6323.164 -> that you have after continue.

6325.394 -> So in this case you could see

6327.625 -> that we have I equal to in case when I is equal to equal

6332.1 -> to 5 We are continuing the loop

6334.5 -> which means the print statement

6336.884 -> for I when I is equal to Phi wouldn't get executed

6340.9 -> since you're continuing it.

6342.6 -> So basically as you could see the News being printed here.

6347.1 -> You can see the 01234

6350 -> and there's no 5 here then we have 6789.

6354 -> So basically what we are saying here is

6356.483 -> when I is equal

6357.499 -> to 5 don't execute the statement within the loop.

6360.635 -> Just continue.

6361.5 -> Just keep it.

6362.4 -> Okay.

6363.3 -> So what a methods in Java So method is

6368.2 -> if you would have written

6369.9 -> function or if you would have used any programming languages

6374.4 -> if you want to perform some operation

6376.517 -> if you want to do something or

6378.287 -> if you want to do something on some particular data,

6381.3 -> you would write a method.

6382.9 -> So basically in Java methods are defines the behavior

6387 -> of a class.

6388.23 -> So remember I told you a class is all

6391 -> about State and behavior.

6393.8 -> So methods are nothing but it defines the behavior of a class.

6398.834 -> So what are methods or method has a group of statements?

6403.1 -> Of course, as I said,

6404.4 -> since it defines the behavior of a class you need to have

6407.8 -> some operations done, right?

6409.6 -> So you define the operations through group of statements.

6413.523 -> It is much more used to have reusability of a block of code

6417.984 -> that minimize redundancy.

6419.884 -> So imagine if you didn't have methods then

6423 -> you have written the same piece of code again and again,

6426.587 -> Say for example,

6427.605 -> you have a method which adds to number right?

6430.3 -> And if we write the piece

6431.8 -> of code to add two numbers directly into the main method

6435.035 -> if you want to write it again,

6436.8 -> or if you want to again add two numbers,

6439.3 -> you will have to write the same piece of code again

6441.8 -> in the main method.

6442.9 -> Whereas if you have a method

6444.596 -> what you would do is you would refactor

6446.9 -> and take this add method or functionality

6449.7 -> which adds two numbers

6451.109 -> into a method and this method could be invoked from anywhere

6454.922 -> within the application

6456.343 -> which is nothing but re usability right

6458.8 -> rather than writing the same piece of code.

6460.9 -> Now, what you are doing is you are defining this add method

6463.846 -> into some other method

6464.982 -> which could be called anywhere within the code.

6467.37 -> So that's about redundancy

6468.9 -> that minimizes redundancy and increases the reusability

6472.5 -> of a code a class can have multiple methods

6475.9 -> as you could imagine.

6477.3 -> You could have multiple behaviors introduced

6480.1 -> into a class which means

6481.7 -> that you would potentially have multiple methods within a class.

6486.1 -> A method returns a null

6487.876 -> or a value using the written statement.

6490.8 -> So basically the intent

6492.173 -> of the method is to perform some operation, right?

6495.3 -> So what method would take is it would take parameters

6498.99 -> and do some operations on these parameters

6501.9 -> and it may

6503.1 -> or may not return something back to the calling program.

6506.6 -> So if you don't want written anything you

6508.9 -> have to return null or

6510.9 -> if you want to return some value you could have say for example,

6514.3 -> you want to return string you would return a string

6517 -> of a method you could have void as well,

6519.9 -> which means that the method is not returning anything back

6523.045 -> to the calling program.

6524.398 -> It is doing something within itself and just

6526.714 -> the control would be back to the calling program,

6529.3 -> but it won't return anything out of the method

6532.1 -> that's about method.

6533.638 -> So let's talk about so what the syntax

6536.484 -> of method So the first one

6539.8 -> that you see so this is a method

6542.261 -> which is public int at Eureka integer a GB

6546.79 -> and it is just concatenating the two strings or two numbers

6551.3 -> that we have sent a cross.

6553.5 -> So basically let's an itemized it

6556.9 -> so what is public so public is nothing

6560.1 -> but again access modifier

6563.5 -> so public means this particular method

6565.939 -> could be accessed from anywhere within the application.

6569.9 -> So that's what public means similarly you

6571.9 -> could have private.

6573.2 -> You could have default scope or you could have protected scope.

6577.6 -> So public is accessible anywhere within the program private is

6582.2 -> within the class default is within the package

6585.7 -> and the protected is within the subclass

6588.465 -> and the package.

6590.1 -> Okay.

6590.9 -> What is this int it is nothing but the return type

6594.479 -> so this particular method is going to take two.

6597.839 -> Arguments and do something and written integer,

6601.3 -> right name of the method is you can see ID Rekha.

6605.6 -> That's the name of the method.

6607.1 -> Okay.

6607.422 -> So what do you see within the parentheses

6610 -> after the method name is nothing but the arguments

6613.5 -> that this method takes so

6616.2 -> what this particular method

6618.095 -> is doing is it is taking two arguments

6620.7 -> which it is acting upon right?

6622.9 -> So it takes integer a and integer B,

6625.9 -> that's the parameter list.

6628 -> So whenever you want to invoke this particular method you have

6631.9 -> to pass arguments in this order.

6635 -> Now, what do you see within this curly braces is nothing

6638.1 -> but the behavior or this is

6640.1 -> how you introduce a behavior to the class or this is

6643.693 -> how you add functionality to a method.

6646.3 -> So what you are doing here is kind of adding

6649.3 -> these two numbers.

6651.4 -> So what is the written statement?

6653.399 -> What does it do?

6655 -> So written statement is nothing

6656.8 -> but you do something you take the arguments

6659.3 -> whenever controlled comes into a particular method.

6662.648 -> It does something

6663.786 -> and you return it back to the calling program.

6667 -> So the written statement is a control flow statement

6670.696 -> that terminates the execution

6672.8 -> of method and written control to its caller.

6676.3 -> So when return type of any method is void,

6679.9 -> then the method does not return anything if it is void,

6683.699 -> you won't return anything out.

6685.2 -> But if it is written in string

6686.7 -> or something you would return string

6688.896 -> or null if you land not to return anything,

6691.531 -> it could be null as well.

6693.6 -> So here we can see a method by the name work

6696.68 -> which is returning void.

6698.4 -> So you can see that it is not taking

6701 -> any arguments as such or parameters,

6703.9 -> but it is just printing out saying

6705.841 -> that I do recall welcomes you

6707.6 -> in the second case you can see it is written integer.

6712.1 -> So it's taking int A and B. Okay,

6716.7 -> and then it is printing out

6719.028 -> and it's returning integer as well.

6722.3 -> So let's write a program sample program to add two numbers

6726.3 -> and we would be writing all this logic within a method.

6730.6 -> So let's start off by defining a class.

6734.7 -> All right.

6735.5 -> So we define a class say calm dot edu,

6739 -> Rica Dot and a typical name for all arithmetic operation glass

6744.4 -> with all arithmetic operation would be calculator, right?

6747.6 -> So I would write it as calculator.

6750 -> For example.

6751.2 -> Alright, so here you can see the naming convention again.

6754.5 -> There's a package which is calm down

6756.9 -> at Eureka and you have a class has calculator

6760 -> and it follows camel casing

6762.1 -> so it starts with upper case followed by lower case.

6766.5 -> So you can see the class is being created here.

6769.3 -> Okay.

6769.9 -> Now what we are trying to do is you are going to have a method

6773.8 -> which takes to number.

6775.8 -> Okay.

6776.7 -> So say I Define let's keep it public.

6780.3 -> All right.

6780.894 -> So this is access modifier.

6782.538 -> We want to keep it public.

6784.067 -> So you want to access

6785.33 -> this particular method from anywhere within the application.

6788.876 -> So I'm keeping this public.

6790.6 -> So typically addition would return results, right?

6794.7 -> You would add two numbers

6796.4 -> and return results of two numbers.

6798.828 -> So that's your written type which is integer.

6802.6 -> So you could either write the return type as primitive

6805.9 -> or you could write it as a wrapper class.

6808.8 -> So basically wrapper class is nothing but integer

6812 -> has its own everything in Java could has to be realized

6816.4 -> in terms of classes.

6818 -> So integer has its own class int is a primitive data type

6823.3 -> and integer that you see here.

6825.992 -> Is a class corresponding int so let's put the return type

6830.8 -> as integer and add is a method name.

6834.5 -> Okay.

6835.38 -> Now this takes two arguments integer arguments,

6839.1 -> which is arg1 and let's put the second one as arg2.

6846.292 -> All right, so we start and ended by curly brace.

6850.2 -> Okay.

6850.7 -> Now we have to write logic within here.

6852.935 -> So what you see here,

6854.17 -> it's throwing an error saying that you

6856.395 -> are not returning integer out.

6858.2 -> There is a missing written statement

6860.278 -> because in the signature this

6862 -> is known as method signature this particular thing

6865.182 -> that we have defined here is Method signature.

6867.8 -> So in the method signature you have mentioned

6870 -> that this particular add method is intended to return integer

6874.5 -> out of the body,

6875.7 -> but still you haven't written integer.

6878.434 -> So basically to get rid of this I could put written null

6882.5 -> which means it's doing nothing now you can see

6885.605 -> that Got rid of the error.

6888.153 -> So let's do one thing just to make it more verbose.

6892 -> I will write integer result is equal to ARG 1 plus ARG 2.

6899.8 -> So this is a method body that you are defining here.

6903.1 -> So you are adding a behavior, right?

6905.217 -> You're giving Behavior to the calculator class.

6908 -> So by defining add method this certain behavior

6911.1 -> that you are introducing now,

6912.811 -> you could have a multiplier method as well

6915.311 -> which would take two numbers and would multiply it

6918.3 -> which is again giving some sort of behavior to calculator.

6922 -> So that's the reason we say

6924.076 -> that methods add Behavior to the plus.

6927.7 -> Okay.

6928.7 -> So here it is taken two arguments arg1 arg2 adding it

6933.3 -> and we will return the result from here.

6937.8 -> All right.

6938.329 -> So this is a method that you have defined.

6940.8 -> But so far we are not invoking this method right?

6944 -> We are not calling this method you want to call

6946.7 -> and check whether it's running as expected.

6949.5 -> So that's where we would have main method right?

6953.6 -> When you type mean it should give you suggestions saying

6957.479 -> that are you trying to write main method?

6960.3 -> So if once you click on it it would this is done by

6962.8 -> IDE by the IntelliJ similarly in Eclipse.

6965.725 -> You would get an option,

6967.3 -> you know, it would give you suggestions saying

6969.3 -> that we want to introduce main method.

6971.4 -> All right, so we have a main method here.

6974.2 -> So again, it's public static void Main

6977.4 -> and it's taking arguments here.

6979.8 -> All right.

6980.6 -> So remember I said static and non-static

6983.3 -> Method you can see here add is non static method

6986.7 -> when it's a non static method you have to create instance

6990.2 -> of this class to invoke it.

6992.339 -> So basically first thing

6994.257 -> that I do is I create instance of Later,

6998.3 -> so how do you create instance of calculator?

7000.7 -> It's with new keyword.

7002.385 -> All right, you create new

7004.3 -> and it would create an instance of calculator.

7007.4 -> Now I give a call to add method

7010.8 -> and suppose I want to add like 10 and 30.

7014.5 -> Okay.

7014.808 -> So these are the arguments

7016.378 -> and it has to be in order in this case

7018.624 -> since both are integer.

7019.804 -> It doesn't matter but had it been some other data type.

7023.169 -> You have to ensure that say for example,

7025.6 -> I write string here

7027.2 -> what this would return is typically a result

7030.664 -> right addition of two numbers.

7033.3 -> Now, let's print it out system dot out dot println.

7039.1 -> This is for printing result

7041.7 -> of addition is flits print out the result

7045.764 -> that we get here.

7047.6 -> All right, and let's end it by semicolon.

7051.7 -> So basically you have a package defined here

7054.1 -> within the package you have calculator

7056.5 -> and actually it's my bad.

7058.4 -> I should have defined it right here.

7061.738 -> So it gives my it gives the right package name here.

7066.1 -> So earlier I had defined

7067.9 -> calculator with income dot Ed u-- Rica again.

7070.347 -> I defined a package computed Eureka which is not required.

7073.7 -> So yeah, you can see here packages calm down said Eureka

7076.7 -> which is nothing but the namespace we

7079 -> have public class calculator.

7081.2 -> So public is nothing but the access specifier

7084.4 -> for this class

7085.5 -> plus is the keyword used for defining class

7088.2 -> and calculator is the name of your class.

7090.5 -> Also one thing to note is the name

7092.8 -> of the Java file should be same as the name of the class.

7096.5 -> So that is something

7098 -> that IDE or IntelliJ would do it for you.

7101 -> You just have to create class and it would create class.

7104.6 -> So basically if you go to the source folder

7107.3 -> you would have something like calculator dot Java right?

7111.3 -> Then you have public method which is again,

7114.3 -> here's the method

7115.197 -> that we have defined public is the access modifier

7117.785 -> for this method integer

7119 -> is the return type add is the name of the method.

7121.8 -> It's taken two arguments arg1 arg2 within the body

7125.9 -> you are adding two numbers and you are returning result

7130.002 -> which is integer

7131.1 -> which aligns to the signature that you have put here.

7134.5 -> All right in the main method just to check

7137 -> whether this add method is functioning properly.

7139.9 -> What you do is you create the instance of calculator.

7143.01 -> You add two numbers you pass two numbers to it then

7146 -> and 30 and we are going to print the results and see

7149.2 -> if it returns as expected.

7151.1 -> So here basically it should print the result as 40

7154.6 -> since adding 10 and 30.

7156.6 -> So remember while it builds it it would compile

7159.978 -> into a class file.

7161.3 -> Okay, the dot Java file would be compiled

7164.036 -> if it's properly written if it's in tactically, correct,

7167.8 -> it would read dot class file.

7170.02 -> All right, let's wait for it to run.

7175.838 -> Okay, so it's prompting me errors

7178.3 -> that we have an other methods.

7180.9 -> So let me do one thing.

7184.2 -> Let me delete other classes that we defined yesterday.

7188.3 -> So I get go to the source folder Comdata.

7191.199 -> Directa.

7192 -> I So I am just deleting this classes

7199.1 -> that we defend yesterday.

7201 -> So that we don't spend time in actually correcting it, right?

7205.6 -> So put it into a backup folder.

7210.6 -> All right, so

7214.7 -> Okay, so we have only this calculator class

7218.1 -> now I run this.

7225.1 -> So yeah, you can see here.

7226.833 -> It has been tested result of addition is 40.

7229.788 -> So basically what it has done is adding

7232.4 -> these two numbers 10 and 30.

7235.2 -> All right, so that's what we have here.

7237.8 -> So we are adding two numbers.

7240 -> So let's talk about the sequence of how all this is being carried

7244.5 -> out by Java right

7245.607 -> when you run a particular program

7247.604 -> how things work out when you run a class.

7250.546 -> The first thing

7251.5 -> that's been called is the main method.

7253.989 -> Okay jvm is nothing but Java virtual machine

7256.98 -> which runs the program for you

7258.988 -> which is part of JRE Java runtime environment.

7262.3 -> When you run a particular class,

7264.182 -> it would search

7265.05 -> for a main method and if it doesn't have

7267.3 -> a main method then it would give you an error saying

7270.3 -> that a class can't be run.

7272 -> So it's pretty much similar to executable file, right?

7275.117 -> So if you're trying

7276.304 -> to run a class it has to have a main method

7278.927 -> or you won't be able to run the class directly.

7281.8 -> So that's where the execution starts from.

7284.4 -> That's the entry point for your program.

7287.2 -> Okay.

7287.7 -> So once it encounters Main

7289.7 -> and everything is good your jvm would start

7292.7 -> executing the statement.

7294.4 -> That are there within your main method.

7296.6 -> Okay.

7297 -> So in the edition case

7298.564 -> that we saw within the main method we invoked we created

7302.378 -> the instance of calculator and we invoked add method right?

7306.5 -> So when we ran that particular class you could see

7309.6 -> that the addition was done.

7311.388 -> So basically what's happening behind the scenes is,

7314.7 -> you know jvm would execute the sequence of statements

7318 -> that you have with a name.

7320.5 -> So again coming back to the example add example So

7324.5 -> within the main you invoke the add method

7327.239 -> right when you invoke add method the control would go

7330.8 -> to the add numbers method

7332.9 -> and it would again execute whatever functionality

7336.5 -> you have put within that particular method this case

7339.5 -> it was addition of two numbers.

7341.4 -> So it would execute once the execution is done.

7344.4 -> It would return whatever is been written out.

7347.769 -> So in this case,

7348.857 -> I was was addition of two numbers,

7351.1 -> so it would return addition of two numbers back to the calling.

7354.5 -> Program so you're calling method

7356.511 -> was the main method wherein you called this add numbers from?

7360.3 -> Okay, so it would come back to the main method and that's

7364 -> how it prints it out.

7365.6 -> So following the invocation of add numbers you could see

7369.308 -> that we have printed out the visual

7371.6 -> that comes out of this add numbers and that's

7374.65 -> how it gets printed onto your console so that

7377.7 -> the sequence of execution that happens behind the scenes.

7382.8 -> Now what are the ways in which you could call a method?

7385.8 -> There's call-by-value call

7387.454 -> by value is nothing but instead of passing the memory location,

7391.398 -> it passes the value of a particular variable.

7394.397 -> Okay.

7394.9 -> So this is similar

7396 -> to call-by-value and call-by-name reference

7398.1 -> that we have in see okay,

7400.2 -> instead of passing

7401.4 -> the memory reference or instead of passing the reference.

7404.808 -> It's just a value that's been passed.

7407.021 -> So if you change something within the method or

7409.844 -> if we change the value

7411.242 -> that's been passed

7412.44 -> within the method only the local copy would change

7415.7 -> whereas the main copy would remain as is

7418.5 -> but basically call by value is just passing the value

7422.1 -> but not the actual reference.

7425.336 -> All right,

7425.836 -> so to understand call-by-value you could so

7429.8 -> this would give you some idea.

7431.942 -> So say for example,

7433.3 -> I have integer ARG 1 which is equal

7437.2 -> to 10 integer ARG 2 which is equal to 30.

7444.099 -> Okay.

7445.4 -> Now I pass ARG 1 comma arg2.

7450.7 -> So what's happening here is it's passed by value.

7453.9 -> So suppose you change.

7455.8 -> What I'm trying to say is here

7458.107 -> if you change arg1 to something else 300.

7463.6 -> Okay.

7464.3 -> So what we are trying to do here is we are trying

7467.4 -> to pass this to arguments arg1 arg2 to add method

7471.934 -> and within the add method we are changing this arg1 200.

7476.2 -> Basically we would check

7478.046 -> whether this hundred is been reflected in arg1 here.

7483.6 -> Okay.

7484.3 -> Arg1 here would change 200 as well.

7488.7 -> Let's see what happens here.

7490.6 -> Okay, so I print it.

7495.3 -> Okay before passing it by value.

7497.8 -> So I print arg1 here.

7500.3 -> Okay, and after I give

7501.992 -> a call I would again printed printing arg1 after busting

7509.7 -> it a value to a method add Method All right,

7515.7 -> so let's run this

7518.5 -> so basically since its passed by value arg1 would remain as 10.

7524 -> Okay, so that's what pass by value is all over.

7527.3 -> So here you can see arg1 before passing was 10 and arg1

7533 -> after passing was again 10.

7535.8 -> Alright, so the change

7537.314 -> that you made here doesn't reflect here.

7540.5 -> So that's pass by value.

7543.5 -> All right.

7544.166 -> So this one more concept of method overloading with in Java.

7548.259 -> You could have same methods

7550.083 -> with different number of parameters same method

7553.238 -> when I say same method it has The same method name

7556.519 -> which would take variable number of parameters.

7559.6 -> Okay, the overloading happens at the compile time itself.

7563.191 -> So during compile-time jvm understands to which method you

7566.836 -> are actually giving a call based

7568.956 -> on the actual parameters you pass on so just to give you

7572.6 -> a fair idea about this I Define one more method.

7578.4 -> C ad which takes say integer arg1,

7584.1 -> let's keep this adders.

7588.4 -> So I defend three parameters here.

7590.6 -> So instead of two I Define three parameters here.

7593.725 -> This is nothing but method overloading.

7596.2 -> All right.

7597.9 -> So here I Define ARG 1 plus ARG 2 plus arg3.

7604.9 -> All right, so we sum it up here

7607.8 -> and we return it back to the calling program.

7613.9 -> So one thing to note here is it's not giving you

7616.7 -> compile time error, right?

7618.5 -> So you can see

7619.2 -> that it has accepted this add method as well.

7622.9 -> So you can see here.

7623.9 -> The signature is pretty much same

7626 -> only thing is we have one more extra parameter,

7629.3 -> which is a RG3.

7630.6 -> So it is treating this true methods as a different method.

7634.2 -> That's what method overloading is all

7636.4 -> about suppose I Define one more ARG pee I say 40.

7645.846 -> Alright, so we have three parameters here.

7649 -> I am giving a call to add arg1 arg2.

7654.8 -> If I put arg1 arg2 the first add method would be called

7659.4 -> if I have one more ARG 3 now the second add parameter

7665.4 -> or the second add method would be called.

7669.3 -> So let's define result from new add method, right?

7676.2 -> So here we say.

7681.3 -> Okay.

7682.5 -> So as I said,

7684.3 -> we have overloaded

7685.428 -> the add method overloading is nothing but same method name

7689 -> but different arguments or different number

7691.6 -> of arguments or it could be different types as well.

7694.6 -> You could have only two arguments but one is integer

7697.912 -> and one is something else

7699.59 -> if for example string

7701 -> that also works so basically different data types

7704.4 -> A number of arguments

7705.638 -> but different data types or different number of arguments.

7709.2 -> Alright, so here we

7710.661 -> are adding three numbers and let's run this.

7715.6 -> So it's going to add 10 30 and 40,

7719.2 -> which is nothing but a tea.

7722.4 -> So this is done at the compile time.

7724.8 -> As I said this linking is done by GBM at the compile time.

7729.2 -> So here you can see results

7731.276 -> from new add methods 80 during runtime.

7734.4 -> You can see that it invoked this particular method

7737.84 -> and not this one.

7739.3 -> Alright now, let's start off with arrays, right?

7743.5 -> What is the concept of arrays?

7746.4 -> So again, this is similar to other programming languages

7750.555 -> arrays are nothing but grouping data

7753.2 -> or grouping values of same data-type.

7756 -> Okay.

7756.6 -> So arrays are used to solve the problem

7759.277 -> of storing multiple elements of the same data type.

7763.1 -> Okay, an array is group of like typed variables

7767.451 -> that are referred to by a common name.

7770.3 -> So you define a name for the array

7772.7 -> and in the future you can use this name to access it.

7776.8 -> Okay specific element in an array is accessed by its index

7782 -> as you could imagine

7783.297 -> since we are grouping you would have multiple elements,

7786.76 -> right you could add something to it

7789.048 -> or you could delete something

7791 -> or you could add it

7792.347 -> to the end insert it in the between of the array

7795.54 -> or just so something

7796.905 -> or just search by index rate you would give some specific

7800.771 -> index and get element from that particular index.

7804 -> So we would be looking at the Which would give

7806.749 -> you a clear idea about this

7808.4 -> but basically array is nothing but group

7810.881 -> of or its multiple elements

7812.662 -> of the same data type array type is fixed

7816 -> and cannot be changed.

7817.5 -> So in Java when you define

7819.377 -> an array you either give the number of elements

7822.7 -> that you can store in the array,

7824.6 -> which is nothing but the array size

7826.6 -> or you have to give the values

7829.2 -> that a particular array would contain right

7831.816 -> when you define it.

7833 -> Okay, but all in all you have to make sure

7836.1 -> that when you define an array you give the size as well

7840 -> which cannot be changed the feature the size

7842.8 -> of the array has to be mentioned during the Declaration itself.

7846.7 -> So here's an example of array this array has around

7850.546 -> for which has four subjects with stores marks

7854.3 -> of four subjects for a student.

7856.6 -> Okay?

7857.4 -> Here you could see indexes in the white box,

7860.707 -> which says 0123 it's always in sequence.

7863.9 -> It starts with 0 and it ends with n minus 1.

7867.5 -> So basically this array is of size for which starts

7872.9 -> from index ranges from 0 to 3.

7875.9 -> All right the value that is stored is nothing

7879.4 -> but the that's a marks in a particular subject

7882.8 -> which is like 87 60 70 and 80.

7886.3 -> That's the value

7887.217 -> that when stored into this array.

7889.3 -> Okay, we can access any

7892.8 -> of this indexes suppose you want to access

7895.9 -> at index 1 you could do it.

7898.8 -> Do you need to define a front you need to Define on the size

7902.733 -> of the array of front?

7904.2 -> This is how it's been done.

7906 -> Okay.

7906.8 -> So this is how you declare array.

7909.8 -> So we saw how we usually declare an integer

7913.2 -> and stuff like that in Java.

7915.322 -> But here we are declaring an array.

7917.9 -> All right.

7918.7 -> So this is an integer array

7921.065 -> and you can see square brackets here.

7924.2 -> Alright, this tells jvm

7926.352 -> that we are trying to Define array of type integer.

7930.423 -> Alright.

7931.038 -> So again, we use the same keyword

7933.412 -> which is nothing

7934.6 -> but Nu new keyword is used to create a particular array.

7939.3 -> All right,

7939.8 -> and here we are defining an array of size five.

7943.1 -> So this is one way of declaring an array.

7945.6 -> The other one would be who initializer itself

7948.7 -> when you declare it you give what are the values

7951.6 -> that particular array is holding up the first case

7954.6 -> you're not giving the values you are just defining an array

7957.8 -> which Those some some amount

7960.015 -> of memory right jvm would reserve some amount

7963.399 -> of memory or in this case.

7965.298 -> It's four bytes right array.

7967.343 -> So for integer, it takes four bytes.

7969.9 -> So it would Reserve 20 bytes for array of size five.

7974 -> All right.

7974.632 -> So in the second case as I said,

7976.681 -> it's directly initializing

7978.325 -> the array it's putting these values directly

7981.084 -> into the memory location still it would be consuming 20 bytes,

7985.1 -> but the second variant would have values

7987.7 -> directly initialized.

7989.3 -> So when you declare an array of size 5 the range

7993.3 -> of indexes would be from 0 to 4.

7997 -> If you try to access index 5 you

7999.7 -> would get this exception exception is nothing

8003.7 -> but a anomalies situation right which or something

8007.6 -> which is not expected

8009.043 -> as occurred in your program

8010.9 -> and Java expresses such event by throwing out an exception.

8015.432 -> You can't access index fi.

8017.6 -> So different ways of declaring an array.

8020.3 -> We saw that it's with new keyword.

8023.1 -> All right, so you have new int 10 which would declare array

8027.2 -> of size 10 again.

8028.6 -> You could either have the square bracket

8031.24 -> at the end of the variable

8033 -> or you could have it in between the type

8035.813 -> and the variable name.

8037.4 -> So behind the scenes it everything is the same.

8041.5 -> It doesn't do anything different for both

8044.073 -> but these are different ways in which erase could be declared.

8048 -> All right, the third one is similar to the last one

8051.9 -> where in we have BR initializing it directly.

8055.5 -> Alright, we are putting this value 12345

8058.484 -> into this array.

8059.9 -> This one is again same you are so within the square brackets,

8064.8 -> you can see

8065.368 -> that you are not defining the size of the array,

8067.8 -> but you have an initializer at the end by which you express

8071.919 -> that you want to put in 1 2 3 4 5 into this array.

8075.4 -> So basically one and two That you see here does the same thing

8080.1 -> it declares the array of size.

8082.3 -> The first case is 10 the second case is five though,

8085.4 -> but behind the scenes it's doing the same thing.

8088.264 -> It's nothing different when it comes

8090.2 -> to actual preserving memory and stuff like that.

8093.202 -> It's doing the same stuff

8094.9 -> and three and four does the same stuff

8097.257 -> only thing is syntactically

8099.061 -> it's varying but what I'm trying to say

8101.6 -> is GBM doesn't do anything different to actually executed.

8106.4 -> So the length of the array is set

8108.7 -> when it is declared

8110.1 -> and when an array is declared array index gets initialized.

8114.761 -> All right,

8115.6 -> so if you define an array and if you try to print the length

8119.1 -> of it you could see that it prints out in this case.

8122.67 -> We have declared an array of size 20 and

8125.413 -> when you do x dot length,

8127.171 -> when you print it out you could see that it prints 20.

8131.5 -> All right.

8132 -> So what are different types of arrays that we have

8135.073 -> again similar to what we have in Programming languages,

8139.5 -> we have single dimensional array

8141.8 -> and multi-dimensional array single dimensional array

8145.5 -> is what we saw earlier like you define array

8149.2 -> of integer of size 5 that is a single dimensional array.

8153.4 -> So in this case,

8154.449 -> you could see a array been initialized with value

8157.6 -> 2 4 6 8 and 10 that's a single dimensional array

8161.8 -> since we have just one dimension one row right?

8165.121 -> Say for example,

8165.921 -> you want to store marks scored by a student

8169.7 -> or marks towed by a particular student just one student.

8173.405 -> That would be a single dimensional array.

8176.2 -> All right.

8177.2 -> So say for example,

8178.8 -> the first one is the marks code in math.

8182.4 -> The second one is the sign and so on and so forth.

8185.595 -> All right, so that single dimensional array.

8189.2 -> So now what's multi-dimensional array so taking the same example

8193.4 -> of storing marks code by a student.

8195.9 -> So by a particular student it would be

8198.2 -> a single dimensional array,

8199.936 -> but suppose you want to show your marks code

8202.7 -> by all the students in all the subjects.

8205.9 -> If you want to store it,

8207.317 -> it would be multi-dimensional array.

8209.376 -> So one particular row

8210.7 -> that you see here would be a mosque secured by a student

8214.9 -> by just one student in all the subjects.

8217.7 -> The first row would be by student won.

8219.741 -> The second row would be by student to the third row

8222.5 -> would be by student 3 and so on right?

8225 -> So that's where you have this application

8227.626 -> of multi-dimensional array.

8229.4 -> So how you access it is nothing

8231.7 -> but you want to access the first element

8234.8 -> the first index it would be a of 0 0

8238.4 -> and this would be of 0 1 and so on so as I said

8242.171 -> if the First Column is for math

8244.661 -> if it's a marks secured in math this entire The First Column

8249.4 -> that you see would be

8251.2 -> marks secured by all the students in math.

8254.5 -> That would be the First Column

8256.6 -> whereas the first row is the Mach secured by student a

8261.087 -> in all the subjects.

8262.8 -> So basically This Could Be Imagined as

8264.905 -> a table in a database,

8266.2 -> right you have a table where in you have rows

8268.9 -> and columns so columns are nothing

8271.45 -> but you have Fields within a table and the rows

8275 -> that you have our different entries

8277.104 -> that you have within a table.

8278.9 -> So This Could Be Imagined in the same way.

8281.3 -> So you could see how the index is you could see

8285.3 -> how the indexes are aligned so X increases

8288.6 -> when you go down and Y increases

8291.009 -> as you go to the right the memory allocation of array,

8295.7 -> so for single dimensional array of type integer,

8299.5 -> 1 integer value takes four bytes, right?

8303 -> So now when you declare an array of size 5,

8306.2 -> you would have 20 bytes Reserve.

8308.6 -> That's how memories been allocated right

8311.4 -> if you have a character array of size 5,

8314.26 -> it would be ten bites

8315.8 -> since each character takes two bites in Java.

8318.9 -> So you would have 10 bytes reserved up front.

8322 -> All right, so that's

8323.206 -> about memory location a location in single dimensional array

8326.8 -> and when it goes to multi-dimensional array

8329.5 -> this case you have like five elements,

8332.4 -> right you have array of 55,

8335.1 -> which means that you have 25 elements stored

8338.02 -> within the array

8339.158 -> right 25 integer element stored within the array

8342.5 -> and each integer value takes four bytes for storage.

8347.238 -> So it would be a hundred bytes.

8349.6 -> All right, so

8350.502 -> if you have array of if you define a multi-dimensional array

8354.6 -> of 5 into 5,

8356 -> you would have basically a hundred bytes allocated for it.

8360.759 -> Let's write some programs

8362.682 -> and understand more about how this arrays operate.

8367.1 -> So we have an array of five elements.

8370.2 -> All right,

8371.141 -> as you could see here 2 4 6 8 and 10 write a program to access

8375.9 -> element at a specific index.

8379.1 -> Okay, so you have an array of five elements 2 4 6 8 and 10

8385.4 -> and we want to access it.

8387.323 -> We want to access particular element.

8390.092 -> All right, so let's write so I create a class.

8395.1 -> All right, I Define this as our a demo,

8399.8 -> so I don't give a package name here

8401.948 -> because I am defining a class within a package

8404.8 -> so you could see here the package came directly

8408 -> because I right clicked here right

8410.288 -> and then created a new class.

8412.3 -> So yeah, you get this particular class here.

8415.507 -> I Define a main method

8417.2 -> as a type main it would give me a suggestion.

8420.7 -> So this is the entry point again for this particular class

8425.2 -> and suppose I Define the jar.

8429.8 -> Ray and suppose I Define 2 4 6 8 and 10,

8435.3 -> right so you could see here.

8437.8 -> We have an array defined of size five.

8441.6 -> Okay, and you have initialized it as well.

8445 -> So what I was trying to say is you need to have length

8448.4 -> of the array given up front right?

8450.503 -> If you don't do that,

8451.842 -> it would show you an error

8453.5 -> so you can do something like array of integers is equal to Nu

8457.4 -> so you could see here array initializer expected.

8461.6 -> All right.

8462.3 -> So either you will have to initialize it

8464.9 -> or give some value to it.

8466.8 -> So if you put here 10 you could see

8469.4 -> that it compiled right?

8471.8 -> So either you will have to mention some indexes here

8475.723 -> or the length size

8477.107 -> of the array or the ways to initialize this okay.

8482.2 -> Now you could see the compilation error as gone.

8485.034 -> So what I'm trying to say is it jvm has

8487.27 -> to know about the size of the array of And

8489.664 -> if it doesn't know then it would flag you with an error.

8493.19 -> All right, so we have defined this array of let me keep it

8497.695 -> as is okay.

8498.8 -> So now we have defined an array of size here five

8503.3 -> and we have initialized values as well.

8506.9 -> Now, let's try to print out values, right?

8510.5 -> So just to keep it simple suppose.

8513.039 -> It ranges the index would range from 0 to 5,

8516.346 -> in this case.

8517.4 -> So this value to is stored

8519.4 -> at index 0 value for is stored at index 1 value 6 is stored

8524.9 -> at index 2 value 8 is stored at index 3

8529.7 -> and then is to that index for all right.

8533.2 -> So let's try to print 0 by the way.

8537.3 -> I want to copy it.

8544.4 -> Yeah, so I'm just sprinting 0 1 and 4 and let's see

8548.7 -> what it gives up.

8550 -> Right so it should print 2 4 and 10, right?

8557.08 -> So you could see here to 4 and 10.

8560 -> Now.

8560.204 -> The other thing that I wanted to show is

8562.7 -> if you try to access so let me show you

8566.497 -> what happens there.

8568.5 -> All right, so

8570.3 -> if you try to access at index 5 which doesn't exist at all.

8576.1 -> No, it should give you a exception So

8580.1 -> in Java exceptions could be

8581.9 -> nothing but God and you could do something with it.

8585.2 -> So here you could see

8586.5 -> that it gives it gave you array index out of bounds exception

8590.217 -> since five doesn't exist at all.

8592.2 -> The index five doesn't exist at all for this array.

8595.3 -> Okay.

8595.7 -> Now let's define multi-dimensional a write code

8599.4 -> to find the length of rho 0 right.

8602.823 -> So let's define a multi-dimensional array.

8608.7 -> Alright, so we have a multi-dimensional array here.

8612.2 -> So how you define multi-dimensional array is

8615.1 -> something like 1 2 3 4 Alright,

8621.6 -> so this is a multi-dimensional array that you have.

8627 -> Okay, so we have defined a multi-dimensional array

8630.4 -> the size of this array would be 2 by 2.

8633.3 -> Right 2 by 2 is the size of this array

8636.3 -> since you have two elements here

8638.2 -> or let me put it to remove the confusion.

8641.5 -> Let me put it this way.

8643.2 -> So right now we have like 2 by 3,

8645.7 -> right so you have like two columns and 3 rows.

8649.5 -> All right.

8650.3 -> So now let's print actually it has to be 3 by 2 rather.

8655.6 -> Okay.

8656.542 -> Now, let's print the size of this array 0 right.

8660.4 -> So how we do it is

8661.9 -> again println now you have multi-dimensional array

8667.5 -> and you have 0

8668.8 -> so 0 to 1 refers to this 0 1 and 2, okay.

8674.7 -> Dot length,

8676.4 -> so as you could see here that individual row

8679.1 -> that you have within multi-dimensional array

8681.8 -> itself is an array is a single dimensional array.

8684.984 -> So multi-dimensional array is nothing but it's a array

8688.5 -> of single dimensional array.

8690.5 -> Okay.

8691.4 -> So let me print here size of first array.

8699.7 -> I miss Plus.

8704.6 -> So as you could see here,

8706.273 -> there was an exception and since there was

8709.5 -> an exception you won't have this particular statement executed

8713.411 -> since there was exception here.

8715.4 -> So basically to execute this particular statement,

8718.4 -> you should handle this particular exception,

8720.971 -> but we are not talking about handing the exception yet.

8724.2 -> So I'll have to comment this to pass through.

8727.4 -> So now you could see

8728.8 -> that it has printed out to which is your size of first array.

8733.9 -> So this is a program

8734.9 -> that we actually did right now create an array having

8738.7 -> many characters write a program to copy elements

8742.3 -> from created array to another array

8744.3 -> and also write a program to delete an element from an array.

8748.2 -> Okay, so I will just talk about this right here.

8752.2 -> So we have an array here of characters, right?

8755.4 -> So basically when you want to delete something from my array,

8758.9 -> what you will have to do is

8760.369 -> you will have to shift the indexes, right?

8762.6 -> You can't delete something directly from an array.

8765.2 -> So what you will have to do is

8766.7 -> if you want to remove something then you will have

8769.1 -> to shift the indexes

8770.4 -> what happens is suppose you have an array of five integers

8774.25 -> and suppose you are deleting the second element right.

8778.015 -> Now.

8778.28 -> What you would do is you would shift

8780.6 -> if you are deleting the second element

8782.8 -> within the array you would shift all the elements

8786.3 -> that follows the second element to the left, right?

8789.7 -> So the third element would become the second element.

8793.017 -> What would become third

8794.469 -> and the fifth one would become the fourth.

8797.006 -> So basically you shift it.

8798.615 -> That's how you delete something from an array.

8801.45 -> All right.

8802.088 -> So other thing is about copying elements from the array,

8805.6 -> we have a utility class

8807.324 -> which is nothing but system system is a class itself.

8811.1 -> So as you could have seen

8812.943 -> that when I'm printing out something I do system dot

8816.573 -> out dot println, right?

8818.2 -> So this system it's a utility class in Java

8821.071 -> where an IT exposes lot

8822.644 -> of functions within a lot of methods utility methods.

8826.619 -> So one of them being our a copy,

8829.3 -> so here you have to give source

8832.146 -> and the starting index and the destination

8835.5 -> and what we are trying to do here is copy 5,

8838.675 -> so this is how we copy

8840.3 -> from one array into another starting from index 0.

8844.8 -> So this is copying and the other one

8847.2 -> that you see here is about delete.

8849.9 -> So as I said deleting is nothing

8852.1 -> but we have A logic written here to shift

8855.2 -> the indexes to the left.

8857.5 -> So here we are trying to delete one at index 3 and we

8861.5 -> are just shifting elements after this index 3 to the left.

8866.2 -> That's how we delete something from an array.

8869.5 -> Now.

8870 -> Let's see what our strings so string is nothing.

8873.9 -> But again the data type with in Java.

8877.1 -> So why do we have strings at?

8878.681 -> All?

8878.9 -> Right.

8879.2 -> We have array of characters then why do we have string at all?

8883.1 -> So here's an example

8884.7 -> where in you have lot of loads of data?

8887.341 -> So you could imagine a role of a data analyst

8890.4 -> who has to analyze through lot of data coming in right?

8893.8 -> So nowadays, it's like petabytes

8895.703 -> of information being processed throughout a day,

8898.5 -> right which would be very difficult to handle

8901.4 -> if you had to deal with character array.

8904.149 -> So that's where that's

8905.712 -> where Java has come up with strings,

8907.839 -> which is nothing but a group of characters,

8910.4 -> but you don't have to deal with it Java

8912.9 -> by Itself has a class

8914.7 -> which would take care of this strings and

8917.5 -> since strings are widely used

8919.395 -> within a program you could imagine that name or anything

8923.049 -> that any identify

8924.197 -> that we have is mostly we have to store it as the string.

8928 -> So one of the data types

8929.729 -> that widely used within industry or which is widely used

8933.756 -> in programming is string, right.

8936.1 -> So Java has some kind

8937.7 -> of string management as well to make sure

8939.7 -> that programs run or make effective use of strings.

8944.2 -> Okay.

8944.7 -> So here what's been mentioned is James is a data analyst

8948.8 -> and he's finding is really difficult to actually deal

8952.5 -> with character array to store patients names every time

8956.9 -> so that's where we have string.

8959.6 -> So string a solving the problem

8961.521 -> of actually dealing with character array.

8964 -> So Java is actually

8965.461 -> having character array is touring characters

8969.1 -> or the characters in the string in a form of character array,

8972.7 -> but It doesn't expose it to the outside world.

8976.126 -> You can just use this class to deal with it,

8979.4 -> but you don't have to deal with character arrays.

8982.4 -> So Java string is nothing but sequence of characters,

8986.3 -> they are objects of type string class.

8990.2 -> Once the string object is created.

8992.41 -> It cannot be changed.

8993.794 -> This is the immutability functionality of java.

8996.711 -> We're in once you write to it.

8998.614 -> You can change the value.

9000.2 -> So this is specifically important when it comes

9003.191 -> to multi-threading

9004.406 -> when you have multiple threads accessing a particular string

9008.487 -> or same string.

9009.5 -> So that's when immutability

9011.5 -> helps us to make sure that you know,

9013.9 -> multi-threading is it's

9015.473 -> thread-safe we call it as thread safe

9017.923 -> because multiple threads can access the same string just

9021.596 -> because it is immutable.

9023.2 -> All right.

9023.788 -> So what are different ways in which you declare a string?

9026.7 -> So you have string Str is equal to new string

9029.5 -> which we are not initializing the value of the string here

9032.8 -> which could Any value and you have string str1 is equal

9037 -> to Ed Eureka wherein you are initializing the value

9040.4 -> of the string right away.

9042 -> The other one is the character array

9044.3 -> similar to the integer array that we discussed.

9047.4 -> We have character array as well.

9050.2 -> So immutability of the string.

9052.487 -> So why do we have immutability one is for security.

9056.214 -> So string stores lot of useful information,

9059.359 -> like even the credentials and stuff like that,

9062.679 -> which shouldn't be accessed by external users.

9066.067 -> So this immutability factor

9068.1 -> of string helps us to keep it secure

9070.8 -> so that no one else can see it synchronization.

9074.4 -> So this is what I spoke about

9076.4 -> when you have multiple threads accessing the same string,

9079.967 -> you don't have to synchronize it Java by itself

9082.832 -> through its immutability feature would ensure

9085.649 -> that multiple threads can access the same string

9088.7 -> without hampering it or it would run

9091.1 -> as it's expected.

9092.8 -> Shing so caching is nothing but you have a string pool.

9096.7 -> So basically if you have two strings with the same value,

9100.5 -> it won't store it.

9102.3 -> It won't store redundant copy of it.

9105 -> There would be just one copy in the string pool

9108.1 -> and both this references would be pointing to that value.

9111.9 -> If you happen to change one of these references it would point

9116.456 -> or it would create a new value in the swimming pool

9120.2 -> and point the other reference to it sort of so basically

9124.43 -> what we do is why caching is required is

9127.5 -> as you could imagine in application,

9129.9 -> as I said string is widely used data type

9133.5 -> and you could have multiple references pointing

9136.807 -> to the same value of a string.

9139 -> So we don't want to have duplicate values stored.

9142.8 -> That's where this caching comes into picture to utilize

9146.4 -> memory efficiently.

9148.2 -> So what is shrinking pool

9150.2 -> as I said string pool is all the constants

9153.5 -> that you define within the string

9155.4 -> within the application would be stored

9157.577 -> in the string pull string tool used in Java is a spool

9160.7 -> of string stored in Java Heap memory.

9163.5 -> So we have heat memory.

9165.3 -> We're in the objects are created and that's

9168.236 -> where string pool resides as well.

9170.507 -> String pool is Possible only because strings are immutable.

9174.5 -> You can't change once it is defined.

9176.283 -> You can change it.

9177.2 -> If you change it,

9178.2 -> then you can change that particular memory location.

9181.415 -> It creates one more entry in your string pool

9184.8 -> and the reference would point to the new entry.

9187.9 -> So the actual memory location is not getting changed.

9191.284 -> That's what immutability is all about string pool helps

9194.8 -> in Saving lot of space for Java runtime.

9198.1 -> We are breaking on the redundancy Factor here.

9201.007 -> So if you have multiple strings

9203.5 -> or if you have multiple strings holding up the same value,

9206.9 -> it won't create.

9207.8 -> People copies of it there would be just one value

9210.623 -> in the string pool,

9211.7 -> which would be accessed by all the references.

9215.6 -> So basically string pool

9217.446 -> as we discussed is or resides in Heap memory.

9222.2 -> So string is not a primitive data type

9224.8 -> unlike character character CH AR

9226.966 -> is a primitive data type string is

9229.261 -> not a primitive data type

9231 -> is the wrapper class to array of characters

9235.2 -> and this is specifically done

9237.43 -> so that Java has a mechanism to manage strings.

9241.6 -> Well, which is widely used it arrived

9244.3 -> within any application

9245.9 -> or any programming language for that matter.

9249.7 -> Della strings are stored in string to love Heap area

9253.5 -> which we already discussed so we can see a string pool.

9257.8 -> So we have stack memory and Heap memory.

9260.4 -> So when you have a local variable when you

9263 -> define something locally,

9264.693 -> the reference is created in the stack.

9267.2 -> All right, and it points

9268.668 -> to the actual object is created in the Heap,

9271.3 -> but the reference is created in the stand

9273.75 -> so you could see as pointing to hello in string pool.

9278.3 -> Okay, so s is nothing

9280.592 -> but a reference reference to this ring.

9284.153 -> Okay, so here we can see that we are concatenating.

9288 -> Right?

9288.5 -> So this would give you fair amount of idea.

9291.836 -> What immutability is all about, right?

9294.696 -> So here we have string S1 is equal to happy.

9298.5 -> All right,

9299.6 -> and what we are printing out the original string

9303.1 -> that is happy, right?

9304.624 -> So you could see here S one is a reference

9307.6 -> that's been created in the stack.

9309.7 -> You have a string pool within your HEAP memory

9312.44 -> which would store all the strings all the constants

9315.485 -> or literals that you have defined here.

9317.8 -> So you could see happy been stored in the string pool

9321 -> and S1 pointing to it.

9323 -> Now you are trying to concatenate S1

9326.136 -> with learning, right?

9327.752 -> So it's happy learning.

9329.6 -> So you could see

9330.861 -> that the memory location that s one is pointing

9334.6 -> to is not changed right still pointing to happy.

9338.4 -> But this one more constant that's been created

9341.4 -> in the string pool that second category.

9343.9 -> The nation of happy

9345.242 -> and learning so you could see happy learning also created

9349.2 -> but what's important to note here is s 1

9352.1 -> is still pointing to happy.

9354.1 -> It's not pointing to happy learning.

9356.9 -> All right, so

9357.9 -> if you want S1 to actually point to happy learning this is

9363.2 -> how you do so you have S 1 which has the value happy.

9367.8 -> All right.

9368.7 -> So you do S1 dot concat learning and you assign it to S 1.

9374.3 -> All right.

9375.1 -> So you are assigning to the same reference as S1

9378.1 -> and you are printing out s 1 in this case,

9381.4 -> what would happen is unlike the previous example

9384.9 -> that we saw there in S1 is still pointing to happy you would see

9389.2 -> that as one is pointing to happy learning.

9392.1 -> So here you could see

9393.6 -> that this one is pointing to happy learning.

9396.9 -> So basically you

9397.8 -> move the reference from happy to have Peter.

9400.7 -> All right.

9402.4 -> So, let's see what our strings how do we operate on strings?

9407 -> Right?

9408.1 -> So let me create a new class here.

9410.7 -> Just ring demo.

9414.3 -> I create a main main method again.

9416.838 -> All right.

9417.9 -> Now what we do is string s is equal to and Eureka.

9424.7 -> All right.

9425.445 -> So let's first print the length of the string.

9429 -> All right.

9429.699 -> So this is how this utility class or this is

9432.7 -> how this wrapper class helps us.

9435.2 -> So it has all these utility methods right you just have

9438.6 -> to do else dot length.

9440.2 -> It would give you length of the string so had we

9442.9 -> not had strings and

9444.066 -> if you want to deal with the character arrays,

9446.829 -> you would have to print the size of the array here.

9451.711 -> Alright, so when we run it,

9454.1 -> it should print it it is the size

9456.7 -> of the string at Eureka.

9459.7 -> Let's have substring.

9463.1 -> So it's a beginning index.

9464.7 -> So suppose we give to

9466.4 -> so it would give you substring from index 2.

9470.5 -> So basically we are getting substring.

9472.607 -> We are getting part of the string substring

9475 -> is nothing but part of a string right

9477.5 -> from from a particular index.

9479.6 -> So since we have given to hear it starts

9482.6 -> from index to so you have 0

9486.1 -> he's at 0 and x

9487.6 -> 0 D is at index 1 and U is at index 2 so it starts from you

9493.3 -> till the end of the string you have compared to you.

9497.6 -> Could Define two strings

9499.018 -> and you could actually compare them and see

9501.5 -> the value so basically So

9505.1 -> you could have one more string defined here

9507.5 -> something of this sort.

9511.4 -> Alright, so here we compare it.

9514.3 -> So we are doing s 1 dot compared to To him, it's true.

9521 -> So we are comparing S1 with S2.

9524.2 -> So it compares the given string with current string.

9527.9 -> So here you can see it as shown minus 1 right

9531.6 -> since B is one ahead of a so

9535.387 -> if you have same string it would show you zero.

9542.6 -> So if it's exactly the same it would give you zero.

9547.8 -> You have he's empty suppose.

9550.3 -> You don't have anything within your spring.

9552.586 -> You could check it whether it's empty.

9554.8 -> He's empty returns a Boolean variable which means

9558.2 -> if it's true it is empty and if it is false,

9561.787 -> it has some value then we

9563.7 -> have to lower case we have to upper case

9566.4 -> in this case suppose you want to have could be scenario

9569.889 -> in which you want to change

9571.633 -> or you want to change the casing.

9573.7 -> So I'll just take one of that I make it to uppercase.

9578.4 -> Okay, so s 1 is nothing

9580.4 -> but we have Ed Eureka stored within and we are so

9584.1 -> when I run this

9586 -> you should have said Eureka printed in uppercase.

9589.9 -> So here we have written camel casing and let's see the output.

9595.8 -> So here you can see the string was converted

9599.022 -> or translated into upper case.

9601.7 -> So similarly you could do lowercase

9603.7 -> which would print string in lowercase.

9607 -> Now we have value of is nothing but the value of a string value

9611.9 -> of some of the data type

9613.455 -> so you could pass integer and you could do value

9616.5 -> of and it would give you a convert integer into string,

9621.4 -> right so value of is a method within string

9624.6 -> which takes different data type and converts it into a string.

9628.3 -> So just to give you an example you could have

9631.3 -> like teacher I is equal

9634.3 -> to a hundred String dot value

9638.7 -> of and you give I it converting this I into string.

9644.2 -> So it would print the same value hundred

9646.583 -> but it's converting it into spring

9649.1 -> you could replace something within the string.

9651.047 -> If you want to replace

9652.147 -> particular character within the string

9653.8 -> which could be done with replace method.

9655.9 -> So replace method takes

9657.594 -> two parameters replaces a method within string

9660.902 -> which takes two parameters.

9662.794 -> First one is the character

9664.6 -> that you want to change and the second one is

9667.624 -> the new character that you want to change replace to.

9671.3 -> Okay so here to show

9675.2 -> S1 dot replace I could replace e Within a be alright,

9684.4 -> so we are making it lowercase and as you can see here,

9689.4 -> it's printed in uppercase E was changed to lowercase e

9693.5 -> so that's about replace.

9696.4 -> We have contains

9697.7 -> which again gives you Boolean type result,

9701.3 -> which says whether a particular value

9703.77 -> of particular character is present in a string.

9706.9 -> All right.

9707.6 -> So in this case we check

9709.5 -> whether we have a stew with a TLD.

9713.7 -> Oh and you replace t with L,

9716.4 -> which becomes hello,

9717.868 -> and now we are checking with the replaced string contains D,

9722.2 -> which it doesn't contain it,

9724.019 -> right so it would give you false.

9726.2 -> So that's about contains equals is basically checks

9730.3 -> for the equality of string.

9732.3 -> It takes one argument

9733.9 -> and it Compares it against the string object

9736.799 -> against which you invoke the equals against.

9739.7 -> All right, so to give you an example,

9742.2 -> so you have S 1 which is at Eureka Eureka now to print it.

9749.8 -> So here we do S1 Dot.

9756.8 -> printing equality of string So

9760.4 -> since it's the same it would give you true

9763.3 -> if had it been different

9765 -> it would give you false.

9767.1 -> So you can see here.

9768.7 -> It's printing both

9770.2 -> the strings are the same you have different methods,

9773.7 -> like compare ignore case

9775.892 -> where in this case we compared with case, right?

9779.8 -> If you would have had Eureka in lowercase, right?

9784.1 -> If it would have start

9785.2 -> with lowercase e you wouldn't have got 0 here.

9788.4 -> All right, whereas this one more method which is s 1 dot

9792.4 -> compared to ignore case

9794.046 -> when it doesn't consider the case, right?

9796.907 -> So even if there is a case change

9799.101 -> if this how one in uppercase and one

9801.5 -> in lowercase still it would match all still

9804.3 -> it would give the value as 0

9806.2 -> which means both the strings are the same we could get

9809.9 -> some character out from a string.

9812.399 -> Okay.

9813.1 -> There is a method character

9815 -> at there's ends with which again returns a Boolean value saying

9819.5 -> that That a string ends with a particular character.

9822.969 -> Alright, so here

9824.2 -> what we are doing is we are checking

9826.9 -> whether the string P

9828.3 -> which holds the value happy learning is ending with you,

9832.2 -> which doesn't right.

9833.509 -> That's the reason it gave you false.

9836.1 -> Had it been G here it would have given it true.

9840.1 -> Now that's about strings.

9841.822 -> Now.

9842.097 -> Let's talk about different variant of strings.

9845.188 -> And why do we need it?

9846.9 -> So there are like three variants

9848.9 -> of string one is the string class itself.

9851.4 -> The other one is stringbuffer and you have a string Builder.

9854.6 -> So we'll talk about why do we need this variance

9857.182 -> at the first place?

9859.034 -> So string buffer is nothing but good for multi-threading

9863.4 -> when you have multiple threads.

9865.597 -> Usually it's good to have string buffer

9868.368 -> because all the reads and writes that you do on the string.

9872.6 -> It is synchronized.

9874.1 -> So when I say synchronized there's only one thread

9877.869 -> that could access a particular method within a class

9881.807 -> at any given point

9883.2 -> so you can't have multiple threads going in

9885.678 -> and changing the value or doing something.

9888.1 -> So basically if you have a string within your application,

9891.3 -> which is been accessed by multiple threads it's better

9894.8 -> to go with stream buffer

9896.509 -> or if there is lot of not accessed as such access.

9900 -> One factor, but of course

9901.5 -> if there are a lot of modifications done

9903.794 -> and stuff like that like with stream

9905.792 -> before you could append a pain to a particular string

9908.8 -> which cannot be done

9909.985 -> in string right in stream buffer.

9912.141 -> You could actually do lot of things it cannot be done

9915.2 -> and string and just to make it thread safe.

9918.095 -> They have made all the methods that modify the string contents

9922.21 -> as synchronized so

9923.425 -> that only one thread can access it at any given point.

9927.1 -> So see you can see insert here right in string.

9930.089 -> You don't have all these methods you don't have methods

9933.6 -> to manipulate the strings in string, right?

9936.7 -> Whereas in stringbuffer you have methods

9939.3 -> to manipulate the strings.

9941.5 -> So when I say strings those are literal strings,

9944.4 -> right not the string class.

9946.4 -> All right.

9947.3 -> So here we have string buffer

9950 -> and we are trying to append something to the string buffer.

9958.946 -> So we define a class we Define stringbuffer.

9966.7 -> So you could have like S1 dot append

9970.8 -> and when you see a pendant you could see

9973.8 -> that it appends any data type.

9976.7 -> This is the important factor in stringbuffer you have lot

9980 -> of utility methods

9981.1 -> within or you have lot of methods to manipulate the string

9985 -> which you don't have within string class.

9988.2 -> All right.

9990.6 -> So this is mutable,

9991.957 -> right you are changing the values suppose.

9994.885 -> I append three exclamation marks do it, right.

10002.7 -> So what we are doing here is we are just printing

10005.4 -> out the new string.

10006.5 -> All right.

10007.6 -> So basically you could you should see at Eureka

10011 -> and the three exclamation marks.

10015.215 -> As you could see here it got upended.

10018 -> So basically it's a mutable string change the value

10021.5 -> with them insert is nothing

10023.6 -> but inserts a new character at the given position.

10027.8 -> So here we are saying that inside w at position zero.

10033.3 -> You could replace it replace particular

10037.288 -> or replace substring with a new string.

10040.9 -> So here what we are saying is replace index starting

10045.3 -> from 0 till to with this new character sequence.

10050 -> You could delete something from it delete sequence of it.

10054.237 -> So here we are saying from index 0 delete one character.

10058.4 -> So if you have two then it would delete two characters.

10061.8 -> So basically when you

10063.138 -> say two characters even this e would have been gone.

10066.388 -> Okay, in this case,

10067.8 -> we are just deleting one character.

10069.9 -> So basically this delete method takes the starting index

10073.7 -> and the number of characters following the starting index.

10077.2 -> Zebras you have like you could reverse the entire string.

10081.5 -> Okay, so just to show you again new string dot

10087.234 -> if I reverse it.

10090.3 -> So basically this is a kind of utility methods

10093.4 -> which we often use right

10095.8 -> so you can see it's been reversed here.

10099.3 -> All right, you can see the capacity

10101.175 -> of the string capacity of the string buffer is nothing

10104.1 -> but I think it reserves 16 characters initially

10107.712 -> when you declare it

10109.2 -> and it keeps on incrementing it

10111.6 -> so it has a growth factor defined within which

10114.547 -> you did not take care of at this point,

10116.998 -> which you did not think about it at this point

10119.9 -> because those are internals to Java but initially

10123.52 -> when you declare a string string buffer storage space

10127.5 -> for 16 characters,

10128.915 -> which is 32 bytes.

10130.6 -> If you have stringbuffer by do we have string Builder, right?

10134.319 -> So string buffer as I said has some drawbacks.

10137.9 -> What are the drawbacks is more about string buffer

10141.394 -> is synchronized when I say synchronized which means

10144.936 -> that only one thread can enter it only

10147.44 -> one thread can process it.

10149.2 -> So basically if you have a multi-threaded application,

10152.651 -> you should go with synchronization

10154.8 -> because synchronization has some overhead, right?

10158.237 -> It has its own trade offs.

10160.147 -> So when you when you synchronized

10162.43 -> what happens is

10163.5 -> when you move out of the synchronized methods

10166.4 -> DVM internally has to do some operations

10169.213 -> which takes some time.

10170.8 -> So basically it's good to avoid synchronization

10174.2 -> and which would make

10175.377 -> the application much more faster and that's

10177.847 -> where stringbuilder comes into picture

10179.905 -> if it's a single-threaded application

10181.826 -> wherein you know that you don't have multiple threads

10184.682 -> which are going to access a particular string

10187.009 -> in that case.

10187.809 -> You should go with string Builder as against ring.

10190.499 -> First because stringbuffer would give you a slightly

10193.854 -> lower in performance compared to stringbuilder.

10196.7 -> Most of the things

10197.794 -> that string buffer does is done by stringbuilder as well.

10201.2 -> As far as the functionality is concerned but it's not thread

10204.782 -> safe stringbuilder is faster,

10206.551 -> but it's not thread safe

10208.016 -> which means that you cannot have multiple threats accessing it.

10211.8 -> All right, so to keep it simple,

10213.8 -> if you have multiple threads accessing or string buffer,

10217.035 -> then you should go with stringbuffer.

10218.975 -> But if you have a single-threaded application,

10221.4 -> you should go with string Builder which would make

10224.001 -> the application much more faster

10225.7 -> than stringbuffer again with stringbuilder.

10228.8 -> The default capacity is 60 when you initialize it stores

10233.5 -> as you could see it allocated 16 space

10237.1 -> for 16 characters initially.

10240.6 -> So as far as the demo is concerned,

10243.2 -> it's pretty much similar to stringbuffer.

10245.416 -> As far as the outcome is concerned.

10247.315 -> It's pretty much similar to stream buffer is no difference

10250.5 -> as such but as far as the performance is concerned

10253.712 -> stringbuilder is faster than string buffer

10256.4 -> because it's not synchronized.

10258.7 -> Okay, so you define a string Builder with happy

10262.597 -> and you append learning to it?

10265 -> Okay, and if you try to print s B1

10268.4 -> which is appended with learning

10270.42 -> you will see happy learning would see it been upended.

10274.2 -> Okay similar to stringbuffer

10276.016 -> when you delete character

10277.639 -> from index position zero and one character

10280.3 -> from that position you would see

10281.9 -> that the H which is the first character has been deleted out

10285.5 -> so you could see

10286.7 -> that at index 1 you could insert welcome.

10289.9 -> You can see the entire string

10292.8 -> that is welcome being inserted between okay,

10297.4 -> then you have reverse Could reverse the entire string

10301.7 -> pretty much similar to string buffer.

10304.8 -> So again, this one is very similar.

10308.323 -> You have you are appending you're deleting then you

10312.169 -> are inserting here you have reversing here.

10315.4 -> This is pretty much similar to what we did for stringbuffer as

10318.625 -> far as the syntax

10319.579 -> and semantics is concerned

10321.037 -> and the outcome is the same as well.

10323.1 -> Just a performance change in terms of speed right?

10327.2 -> So, when do you stringbuffer and stringbuilder as I said

10330.946 -> if you have multiple threads you

10333.126 -> should go with string buffer to make it thread safe,

10336.9 -> but it would be slower as compared to stringbuilder.

10340.2 -> Okay stringbuilder is

10342.4 -> specifically good enough and you have single-threaded application

10346.5 -> and it would be faster

10348.04 -> since it's not synchronized.

10350.3 -> So to make it thread-safe you have synchronization

10353.371 -> which adds over it

10354.5 -> to the performance which takes tool on the performance.

10357.3 -> That's why stringbuffer is slower why to use

10361.491 -> object-oriented Concepts?

10364.1 -> So let's talk about classes and objects.

10367.7 -> So classes are nothing but it has got a street

10371.161 -> and behavior right

10373.238 -> as you could see you have a class

10375.7 -> and you have different objects, right?

10378.5 -> There's a phone which is a class and

10380.72 -> which has got different types of phones right rotary phone.

10384.4 -> Then you have a touch-tone phone and you have a cellular phone

10388.4 -> this are objects basically, right?

10390.4 -> So you define phone which is pretty much Jen Rick

10393.591 -> and which has got State and behavior class is something

10397.137 -> that is generate

10398.145 -> that has got State and behavior but objects is something

10401.965 -> that is an instance of a class

10403.884 -> which would have specific State and behavior.

10406.7 -> So phone by itself phone is a Class by itself.

10410.023 -> Which may or may not have specific behavior,

10413 -> but you could see

10414.133 -> that the specific phones will have its own behavior

10417.466 -> to could Define its own behavior.

10419.7 -> So all these three things

10421.406 -> that you see here three types of phones

10424.1 -> and nothing but objects objects of one class state is something

10429 -> that is defined by instance variables, right?

10432.961 -> It's a class level variable right at the class level

10435.961 -> you define something

10437.5 -> that gives State and behavior is nothing but something

10441.249 -> that is defined by methods like calculator was a class

10445.3 -> where in we had add method and add method

10448.6 -> basically gave some Behavior to the calculator class, right?

10453.5 -> So what are attributes so you have a class

10457.4 -> and you have attributes attributes

10459.7 -> and nothing but a property of object and in Java,

10463.323 -> this is defined by your instance variables basically class

10467.6 -> will have properties which is nothing but the state

10471.4 -> which would be defined by instance variables

10474.5 -> and you could imagine

10475.906 -> every instance will have its own set of properties.

10479.3 -> It won't be the same right in terms of the phone

10482.686 -> that we saw earlier.

10484 -> There were three different types of phones you could imagine

10486.95 -> that it would have different properties right?

10489.4 -> It's not the same.

10490.6 -> So what are the naming conventions in generally used

10493.5 -> at the industry level for Java.

10495.4 -> So this is not something

10497 -> that is actually taken care by compiler.

10499.86 -> So even if you follow

10501.4 -> this naming conventions still the compiler would pass through

10505.2 -> but these are best practices

10507.1 -> or this is good to have thing in the industry conventions

10511.1 -> is more about to keep On the same page and make it easier

10514.878 -> for other developers to understand more right

10517.716 -> or keep things simpler.

10519.2 -> So that's why we have conventions.

10521.141 -> If you wouldn't have conventions then people would prefer

10524.1 -> to write in their own way

10525.9 -> which would make us difficult to understand.

10528.5 -> Alright.

10529.2 -> So for class name it start with uppercase

10531.9 -> as we saw in all the examples you would see

10534.9 -> that I have always used started with the uppercase

10538.3 -> or it's rather camel casing.

10540.3 -> So in this case you could see stringbuffer demo, right?

10544 -> So it starts with upper case you have B,

10546.457 -> which is again upper case you have B,

10548.807 -> which is again uppercase.

10550.3 -> This is nothing but camel casing it starts with upper case.

10554.3 -> Basically it follows

10555.6 -> camel casing interface name is again similar to class.

10559.9 -> It starts with upper case you have method name

10563.38 -> which would be lower case always

10565.5 -> which should start with lower case,

10567.818 -> but you could have it follows

10569.757 -> camel casing but it has to start with lowercase.

10572.9 -> So maybe it's a predefined method with in Java.

10575.4 -> Right?

10576.1 -> So you could see main starting with lowercase

10579.4 -> or I created a dry Tad

10582.1 -> is again put C uppercase.

10584.692 -> If you would have say for example at numbers

10588 -> you would have something of this sort adverse.

10592.8 -> If you want to append numbers to it,

10594.858 -> it should start with uppercase.

10596.6 -> So basically it's camel casing but starting with lower case

10600.6 -> where as class name.

10601.925 -> It's a camel casing

10603.187 -> which starts with upper case variable name is

10606.81 -> again camel casing we should start with lowercase

10610 -> and constant is always

10611.676 -> like it has to be everything in uppercase.

10614.9 -> So basically if I Define a constant final string,

10619.3 -> I would write something like this.

10624.7 -> okay, so and if you want to add more words to it,

10628.6 -> it should be like this underscore

10633.2 -> So it should be separated out band score.

10636 -> All right.

10636.5 -> So these are the conventions

10637.9 -> that followed in Industry by Java community.

10640.8 -> So mostly even if you go to the source code

10643.3 -> if you want to see something dig into the source code

10645.9 -> of java you would see

10647.209 -> same naming convention being followed types of variables.

10650.7 -> We spoke about the types of variables again to brief you

10654.155 -> through we have local variables local variables are nothing

10657.8 -> but the variables that are defined in a method.

10660.8 -> So if you define something within a method

10663.842 -> that's local variable

10665.413 -> so ARG 100 or suppose I Define and T local

10671 -> where is equal to a hundred.

10673.261 -> So this is a local variable right?

10675.8 -> If you remember this is within the scope of a method

10678.845 -> once the control goes

10680.1 -> out of a method your variable is no longer accessible

10683.9 -> and also it gives space for the jvm for garbage collector

10689 -> to kick in and clean up this particular memory space.

10693.2 -> Variables are nothing but it's defined

10695.5 -> at the instance level so here for that matter.

10698.6 -> This constant is also instance variable.

10701.9 -> All right, so I can Define integer

10707.1 -> variable starts with lower case and it follows camel casing.

10711.3 -> So this integer is nothing but an instance variable.

10714.7 -> It's at the class level right when your class is loaded

10718.3 -> when you refer to this particular class,

10720.8 -> you will have your instance variable initialized by Java.

10725.8 -> So instance variables are declared in a class,

10728.5 -> but outside a method Constructor or any block.

10731.6 -> Okay class variables are nothing but static variables

10735.6 -> and it is one copy per class.

10738.9 -> So as against instance variable, which is one per object,

10743.407 -> whereas static variable or class level variable

10747.6 -> are it's just one per class.

10750.826 -> So if you define static,

10752.7 -> this is just one per class and this could be accessed

10757.211 -> directly using calculator calculator dot constant example,

10761.9 -> you would be able to access it but for instance variable,

10765.7 -> you need to have an object created.

10767.867 -> This is non-static basically non static instance variable.

10772.2 -> So one of the reasons why you need to access

10775.03 -> instance variable is

10776.311 -> because different instances might have different values

10779.772 -> for a particular instance variable, right?

10782.4 -> I could Define calculator one right?

10786.2 -> Let me put it as calculator

10790.092 -> and we have like normal calculator.

10795.8 -> You could have one more class which is

10797.881 -> like scientific calculator.

10800.5 -> It's one more object.

10805.8 -> Now a normal calculator can have its instance value

10809.8 -> as 10 and scientific

10811.8 -> calculator can have

10813.201 -> its instance value as a hundred you have different values,

10817.596 -> but whereas in static since it's one per class,

10820.9 -> it's not at the object level.

10824.1 -> So you have mod is equal to new demo,

10827 -> which is an instance of a class demo.

10829.5 -> And you print message right

10831.9 -> d dot print message and it should print this message.

10835.4 -> So basically there's a class demo

10837.861 -> which has got a method print message

10840.7 -> and we are trying to invoke that message

10843.3 -> from the main method.

10845.3 -> Okay, let's talk about the constrictor constrictor is

10848.5 -> nothing but when you invoke new keyword new calculator,

10852.512 -> there is a Constructor implicit Constructor for each class,

10856.693 -> which is without any parameters.

10859 -> So we'll talk about that.

10860.615 -> But when you do new calculator,

10862.6 -> basically there's a method

10864.322 -> which could be used by the programmers to initialize

10867.7 -> variables if they want to initialize something.

10870.72 -> So for each instance,

10872.1 -> if you want the same value for instance variable,

10875.248 -> you could initialize it with in Constructor.

10877.9 -> So basically Constructors are for initialization or

10881.211 -> if you want to do some kind

10883 -> of pre-processing break on invocation

10885.5 -> if you want to initialize something or do some kind

10888 -> of pre-processing

10889 -> that could be done through Constructor Constructor is used

10892.8 -> in creation of an object.

10894.698 -> It is a block of the code used to initialize an object.

10898.8 -> So when I say initialize an object,

10901 -> it's nothing but initialize some property or variable

10904.866 -> within your class Constructor

10906.984 -> must have the same name as the class.

10909.613 -> It is in and it does not have any return type.

10912.9 -> So unlike method,

10914.3 -> which has got a return type Constructor won't have

10917.282 -> a return type at all

10918.5 -> because what we are trying to do

10920.389 -> through Constructor is just to initialize objects

10923.224 -> within but you can't return something out of it.

10926 -> So basically you Constructor is a special method

10928.8 -> which you don't have control

10930.2 -> over you are not doing anything within it you're not trying

10933.377 -> to actually return something out of it,

10935.6 -> right?

10936.1 -> You don't have control over its invocation.

10938.9 -> It's done by jvm itself jvm calls this special method

10942.901 -> when you invoke knew

10944.7 -> or when you create an instance of it by using this new keyword

10949 -> Constructors are of two types default Constructor

10951.7 -> and parameterised Constructor.

10954.6 -> So when I say default Constructor

10957.2 -> and parameterised Constructor,

10958.999 -> this is nothing but so I am defining

10961.4 -> a Constructor now calculator

10964.4 -> as I said, it has to have the same name as the class.

10968.1 -> Okay.

10968.8 -> So this is a Constructor.

10970.8 -> And as I said,

10971.8 -> this could be used for initialization of variables.

10975.1 -> Say I initialize this 200.

10977.5 -> So for all the objects you would see this

10980.7 -> being initialized to 200.

10984.3 -> That's the initialization.

10985.9 -> Okay, so I have created two instance of it to instance

10989.174 -> of calculator class

10990.348 -> that is normal calculator and scientific calculator.

10993.8 -> Let me do normal calculator dot instance variable.

11002.715 -> Okay.

11003.1 -> So here we are printing the value of the instance variable.

11006.9 -> Let me copy the same thing again,

11009.3 -> but in this case.

11012.6 -> the second case I would be As you could see here.

11024.9 -> We have a Constructor.

11026.2 -> I defined a Constructor here Constructor for a class

11029.326 -> which is initializing the instance variable

11031.9 -> to Value 200.

11032.706 -> So as in when you call this new calculator a new instance

11036.049 -> of calculator would be created.

11037.9 -> The first thing that would be called.

11039.905 -> Is this Constructor and which would initialize it.

11042.788 -> So basically what we are trying to do here is we are right

11045.999 -> after the construction of this particular object.

11048.601 -> We are going to print the values of instance variable to see

11051.8 -> if it assigned 202 it.

11056.076 -> So here you can see the value 200 being printed out.

11060 -> So basically if I wouldn't have

11062.3 -> Constructor then the value wouldn't have been 200.

11065.257 -> So let me comment out this one.

11067.228 -> This is how we comment in Java.

11069.191 -> By the way.

11069.9 -> This is a block comment which starts with Slash

11073 -> and asterisk and which ends with asterisk and smash.

11077.2 -> So I commented out that one I comment out the Constructor

11081.2 -> and you would see the value being initialized to 0

11085.1 -> so you could see value been initialized to 0.

11088.5 -> All right, so that's what Constructor is all about.

11092.3 -> Now.

11092.575 -> This is a default Constructor.

11094.643 -> You could have parameterised Constructor,

11097.4 -> which is like integer you provide some value right

11102.1 -> and you assign this value to variable.

11105.6 -> So instead of hard-coding this value of 200

11108.336 -> for the instance variable you could pass on some value

11111.789 -> during the construction of the object.

11114.2 -> So basically what we are doing here is I pass 30 here

11120 -> and bypass 40 here.

11122.361 -> Alright, so I am passing 30

11124.592 -> and I'm passing 42 the Constructor.

11128.1 -> And as you could see here,

11130.2 -> we are initializing the instance variable

11133.861 -> to that value.

11135.2 -> So basically for normal calculator,

11137.815 -> it should be 30 and for scientific.

11141.356 -> It should be 40.

11144.6 -> Yeah, as you could see here you have 30 and 40

11148.2 -> min printed out and this is the parameterised Constructor.

11151.3 -> That's what this default and parameterised Constructor

11155.29 -> and that's what it is all about.

11157.7 -> So default Constructor is you don't even have

11160.847 -> to specify any Constructor.

11162.753 -> So I commented this calculator constructed still implicitly.

11166.8 -> There is the Constructor put in by jvm,

11169.4 -> which is the default Constructor.

11171.2 -> So it's not mandatory to have Constructor each time

11175 -> unless you want to initialize something.

11176.95 -> So what's the difference between Constructor

11179.168 -> and Method constructive must not have a return type?

11181.8 -> Whereas method may or may not have a return type

11185.3 -> here you could see that unlike the methods add integer,

11189.5 -> which return something.

11191.048 -> This doesn't say anything.

11192.6 -> This doesn't return anything

11194 -> because we are not doing anything within it.

11196.3 -> You're just initializing

11197.9 -> it initializing some instance variables right Constructor name

11202.147 -> must be same as the class

11203.888 -> so that This is a contract this has to be followed

11207.246 -> Constructor has to have same name as the class,

11210.4 -> since you are not invoking the Constructor by yourself.

11213.886 -> It's done by the jvm.

11215.254 -> You don't have control over invocation of Constructor

11218.714 -> and you have to follow the naming pattern that Java

11222.1 -> recommends to or Java forces us to you have to make sure

11225.9 -> that instructor is given the same name as the class name.

11229.719 -> Whereas method can have any name

11231.873 -> as we saw the add method you're free to use whatever method name

11236.039 -> that you want to Constructor

11237.813 -> is used to initialize the state of an object.

11240.6 -> We saw the instance variable being initialized

11243.4 -> within the Constructor method is basically it gives

11246.9 -> some Behavior to a class right

11249.4 -> we saw add method

11250.8 -> which is giving some Behavior to the calculator method,

11254.062 -> which is nothing but adding up two numbers.

11256.7 -> Similarly.

11257.2 -> You could have multiplied you could have divided

11259.5 -> and stuff like that

11260.5 -> which adds more Behavior to it Constructor is invoked.

11264.601 -> Implicitly so you

11266 -> don't have control over invocation of Constructor,

11269.3 -> which is done by Java itself.

11271.2 -> When you try to instantiate a class

11273.569 -> or when you use the new keyword,

11275.803 -> it's implicitly invoked by Java by jvm.

11278.869 -> Whereas method you have to invoke it manually.

11282.4 -> So basically when you

11283.9 -> do this Constructor is called by itself.

11286.678 -> Whereas when you want to call add numbers,

11289.6 -> you have to invoke it explicitly.

11292.3 -> How does Constructor work the moment object of a class

11295.748 -> is created The Constructor of the class is called

11298.6 -> which initializes the class attributes, right?

11302 -> So we saw about this.

11303.315 -> So when you use the new keyword jvm by itself would give a call

11307.2 -> to the Constructor

11308.32 -> which could be used for initializing

11310.5 -> initializing instance variables within your class.

11314.6 -> So type of Constructors

11316.3 -> this default Constructor and this parametrize Constructor,

11319.683 -> which we already spoke about the Constructor,

11322.298 -> which is created by the compiler

11324.2 -> without any parameters is the default Constructor

11327.3 -> and the Constructor with specific number

11329.914 -> of parameters is called parameterized Constructor.

11333.5 -> So here we spoke about this already.

11336.2 -> So we have integer value, right?

11338.7 -> This is a parameterised Constructor,

11340.694 -> since you are passing parameters to the Constructor,

11343.6 -> whereas if you don't Define anything Java by itself,

11347 -> so in this case you could see that we didn't have

11350 -> a Constructor for this class straight.

11352.105 -> I read them all we don't have Constructor for this class.

11355.5 -> So Java by itself puts her default Constructor

11359.5 -> for array demo,

11361.1 -> which is known as default Constructor.

11363.5 -> So it's not mandatory

11365.2 -> that you need to have Constructor every time

11367.864 -> since Java takes care of it.

11369.6 -> That's the differentiation between default Constructor

11373.084 -> and parametrization.

11374.9 -> We use parameterised Constructor

11376.957 -> for passing values to the Constructor

11379.3 -> and initializing something based on the value

11382.197 -> that's been passed out past in brother.

11385.6 -> So the default Constructor is used to provide

11388.509 -> the default values

11389.7 -> to the object like 0 null depending on the type right

11394.1 -> when I didn't have any Constructor at all

11396.3 -> for a moment.

11397.108 -> I am going to comment this.

11398.788 -> So this is a line comment when you put two slashes.

11401.9 -> It's a line comment.

11404.1 -> Okay, it's commenting just

11405.57 -> this particular line This is a block comment

11408.1 -> and this line comment block comment is slash asterisk

11412.2 -> and ends with asterisk.

11414.5 -> / whereas line comment is two slashes forward slashes.

11419.7 -> Okay.

11421.2 -> So basically a comment or disc instructors as well.

11428.1 -> Alright now we have this calculator class now lets me.

11434.4 -> Let me print the value of the instance variable.

11439.7 -> value of instance variable initialized

11445.7 -> by default Constructor.

11450.5 -> All right, so we don't have a Constructor at all.

11452.6 -> So that's what I am trying to say here.

11454.5 -> I commented out this Constructors, right?

11457.5 -> So we don't have a Constructor at all.

11459.84 -> And when you create a new calculator jvm

11462.404 -> by itself would have a default Constructor

11465.1 -> which is used by jvm to initialize variables within

11469.3 -> so you would see

11470.6 -> this instance variable has zero value as 0 because that's

11475.1 -> what the default Constructor does.

11477.5 -> It assigns some value to it has like specific values

11482 -> for integer it 0

11483.919 -> if it's a class it would be null

11486.8 -> so you could see the value being printed as 0 if it's a class

11490.593 -> it would assign value null.

11492.3 -> So in this case you have string right and you could see 0 null

11497.5 -> depending on the type of instance variable

11499.718 -> that we are dealing.

11501.1 -> We saw how we pass parameters and initialized it.

11505.3 -> Constructor overloading is just like method overloading

11508.554 -> without written type Constructor overloading

11511.455 -> in Java is a method of having more than one Constructor

11514.723 -> with different parameter lists.

11516.9 -> Like we defined add we had

11519 -> to add methods and now I have renamed this to add numbers,

11523.484 -> but basically this was add method right

11526.3 -> so you could have multiple methods with the same name

11529.7 -> but different parameter lists,

11531.521 -> which is known as overloading similarly for Constructor.

11535.358 -> You could have the same Paradigm.

11537.3 -> So basically what we are trying to do here is

11539.94 -> we have a Constructor with 1 parameter

11542.241 -> that sing teacher I'll Define one more Constructor here

11545.6 -> with two parameters.

11548.5 -> So we Define one more parameter here and I say for example,

11552.961 -> I put something like this.

11556.4 -> So we are adding up these two parameters

11559.324 -> and putting it into instance variable.

11562.6 -> Okay, this is Constructor overloading.

11565.5 -> So here you have single parameter been passed here.

11568.779 -> You have multiple parameters being passed So

11571.6 -> based on whatever you pass here suppose I say 10 and 20.

11577.2 -> Or say I say?

11580.1 -> So on construction you

11582.2 -> should C-130 as the value of the instance variable.

11592.1 -> Okay, as you could see here,

11594.2 -> you have the instance variable initialized to 130,

11597.5 -> which is nothing but edition of hundred and ten and twenty

11600.894 -> and you could have something like this just hundred and ten,

11604.386 -> which is also K

11605.302 -> because you have a single distinct defined

11607.806 -> as well Constructor taking a single value as well.

11610.9 -> And in this case,

11611.958 -> it would be just a hundred and so Constructors are nothing

11615.4 -> but methods which helps in construction of object.

11620.4 -> All right, so you get a hundred and ten here?

11624.5 -> So Constructor overloading is in Java is a technique of having

11628.149 -> more than one Constructor with different parameter lists.

11632.476 -> So we had a demo about it

11634.5 -> as I showed there were multiple Constructors

11637.3 -> one with one parameter

11638.628 -> and the other one with integer parameters

11641.145 -> and during runtime based on whatever you

11643.6 -> pass a particular instructor would be called in this case.

11647.345 -> You could see

11648.2 -> that in the first case

11649.99 -> which is shop s 1 you could see the first Constructor

11653.99 -> been called which has two integers as being passed.

11658.2 -> Whereas when you create

11659.9 -> object S 2 which has two integer parameters

11662.8 -> and one string you could see

11664.555 -> that second Constructor is being called.

11668.3 -> What's Constructor chaining so Constructor chaining

11671.5 -> is the process

11672.2 -> of calling one Constructor from another Constructor with respect

11675.605 -> to the current object?

11676.9 -> The real purpose of Constructor chaining

11678.75 -> is to pass parameters to a bunch of different Constructor,

11681.8 -> but the initialization

11683 -> should be done at a single place Constructor chaining can be done

11687.5 -> in two ways within the same class from the base class

11691.3 -> and Constructor chaining occurs through inheritance.

11695.2 -> So basically for Constructor chaining,

11697.2 -> there are two key words that we have.

11699.4 -> So one is this this itself is a keyword

11702.5 -> in Java this pH is this is a keyword

11706.035 -> and the super keyword.

11707.953 -> Let's see how we how we do it for this particular Constructor.

11714.8 -> I have this Constructor which has this value, right?

11720.1 -> So instead of doing this directly,

11722.41 -> what I could do is so here.

11724.3 -> I was initializing this value directly

11726.567 -> to the instance variable.

11728.1 -> What I could do through Constructor chaining

11730.8 -> as I could do this

11733.2 -> and I could pass the value comma zero.

11738 -> So basically you're chaining here, right?

11740.1 -> You could see

11740.87 -> that what I am trying to do here is I am trying

11743.6 -> to invoke this Constructor from this Constructor.

11747.1 -> That's what the chain is all about.

11749.3 -> So when you say this it tries to find Constructor

11753.327 -> within your class

11754.7 -> which takes two parameters to integer parameters

11757.9 -> and this is the one it finds out, right?

11760.3 -> It has two parameters.

11762 -> And basically what we are doing is we are keeping

11765.222 -> the second parameter is 0

11766.9 -> which means it would initialize the instance variable

11770.342 -> to whatever value you have here,

11772.6 -> right?

11772.9 -> This is what Constructor chaining is all about.

11775.3 -> It's more about calling Constructor of the same class

11779.5 -> within the Structure of the same class.

11781.6 -> So basically from this Constructor you are giving

11784.188 -> a call to this Constructor that is constructive change.

11788.238 -> Super should be the first

11791.011 -> it gives a call to the super Constructor.

11794.6 -> So you have a subclass and superclass, right?

11798.05 -> What do you do here is you give a call to superclass?

11802.8 -> For Constructor chaining.

11804.049 -> I think they should be good enough

11805.7 -> where and you use this keyword to call Constructors

11809.311 -> within the same class.

11811.7 -> You basically chain them together, right?

11814.3 -> We have demonstration on Constructor chaining here.

11818.3 -> When you create student you could see there's a Constructor

11822.1 -> without any parameter

11824 -> and we could see this Meghan been called.

11828.7 -> So basically what we are trying to do here is the default name

11833.2 -> would be Meghan, right?

11835.923 -> So and again we have one more Constructor,

11839.1 -> which is overloaded Constructor,

11840.8 -> which takes name

11841.925 -> and in that case it would give a call with the specified name

11846.2 -> and Mark as 70.

11847.4 -> So basically 70 is a default marks

11850.2 -> that we are signing and you can is the default name here.

11854.4 -> If you don't provide name, it would be Meghan.

11858 -> All right.

11858.8 -> So this is what Constructor chaining is all about.

11864.1 -> Static keyword static keyword again,

11867 -> we have spoken about in couple of instances,

11869.675 -> but I'll just walk you through this slide again.

11872.6 -> The static keyword is used for memory management static

11876.6 -> is non access modifier used in Java accessible applicable

11882.2 -> for blocks methods class variables static keyword

11887.5 -> is used to refer the common properties of an object.

11891.109 -> So as we spoke it's at the class level,

11893.8 -> it's not at the object level.

11895.8 -> We have it common across all the objects right

11899.7 -> when the static keyword is used to declare any parameter.

11903.45 -> Then memory is allocated only once for that parameter.

11907.4 -> So in this example,

11909.2 -> we could see that since it is one per class.

11912.8 -> So you would have this constant example

11915.934 -> Define just once right it would be allocated.

11919.2 -> Just once whereas the non-static ones like this in.

11924.1 -> This variable you would have memory allocated

11927.646 -> for each and every instance.

11929.8 -> So basically for this instance,

11931.7 -> you would have memory allocated for this instance variable

11935.1 -> for again this normal calculator

11936.992 -> that we had earlier you would again have

11939.3 -> a memory allocated for instance variable.

11941.8 -> All right, so it's one per object

11944.4 -> whereas the static ones are one per class.

11948.9 -> So yeah memory is allocated only once for that parameter.

11953.4 -> All right.

11954.1 -> So here we can see

11955.3 -> that this we have a static string company

11958.7 -> which has some company named put in there

11961.4 -> and we are just displaying it

11963.9 -> right we can see

11965.3 -> that we are displaying ID salary and Company and you could see

11969.8 -> that for both the instances for even and E2

11973.4 -> you have two employees here

11975.4 -> with ID 25 and salary 25,000 and we have employee

11981.8 -> to with salary 30.

11984.5 -> Sorry with ID 30 and salary 3000 right?

11988.5 -> So we are defining two instances of employees

11991.681 -> and you can see here.

11993.2 -> We are not passing the company name as a parameter

11997.3 -> to the Constructor right still

11999.9 -> when you display it look at the output at the right side.

12003.8 -> You can see

12004.487 -> that it has displayed twenty five twenty five thousand

12007.8 -> and SRT Traders the company name came by itself

12011.7 -> because it's one per class.

12014.3 -> So what we are assuming is

12016.5 -> this class is basically designed just for one company,

12020.9 -> right that is SRT creators.

12023.3 -> So all the instances

12024.6 -> of the class are all the employees

12026.7 -> that you create here.

12027.9 -> All the instances of employees

12029.4 -> that you create here will have the same company name

12032.4 -> that is defined here

12033.921 -> since it is one per class.

12036.3 -> Whereas their ID and salary would be variable

12040 -> which would differ as

12041.3 -> per the value that you passed to the Constructor.

12043.9 -> here we can see that company is

12045.6 -> a static variable little allocates memory only once So

12049.467 -> here it could be seen

12051.005 -> that you as I mentioned earlier you have reference variables

12055.328 -> being created out in the stack.

12057.6 -> And in the Heap memory,

12059.325 -> you could see values being stored.

12061.9 -> So ID is tri-five salaries 25,000 for E2 ID is 30

12068.9 -> and salaries 3000 and you can see the static variable.

12073.9 -> So basically static variable is stored in a different space

12077.478 -> which is permanent generation memory.

12079.7 -> That's where the static variables are stored.

12083.2 -> So method could have static as well.

12086.2 -> When a method is static you did not create instance

12089.683 -> of a method to call that method instance

12092.4 -> of a class to call that method pretty much similar

12096 -> to static variables, right?

12098.7 -> So basically I can have one more static method here.

12104.3 -> So say for example I have private static all right,

12110.8 -> so So what I was trying to say here is you

12119.9 -> could have calculator. .

12124 -> And you could directly call the display method.

12127.9 -> So you do not have instance

12129.845 -> of a class created its at the class level.

12132.861 -> This is at the class level rather write one per class.

12137.8 -> Let's talk about this keyword

12140.03 -> that this keyword is used as a reference variables

12143.8 -> to the current object.

12146.2 -> So basically what what it is trying to say here is so

12153.6 -> if I want to print something here,

12155.963 -> let me print the instance variable, right?

12161.4 -> So within the add method

12162.9 -> what I am trying to do is I am printing the value

12165.8 -> of instance variable Within add numbers, right?

12175.6 -> So I'm trying to print the value

12177.2 -> of the instance variable within add numbers

12180.7 -> which would be basically this is

12183.084 -> where we are calling at numbers.

12185.2 -> So basically it should be a hundred and ten, right?

12189.3 -> When we have such scenarios

12190.888 -> where and we refer to an instance variable

12193.5 -> within a method we could see here printing the value

12196.7 -> of instance variable within add numbers gives

12199.547 -> you a hundred and ten right the implicitly

12202.2 -> what happens is

12203.3 -> it puts this dot here this dot instance variable.

12208.2 -> All right.

12208.7 -> So what we are trying to say is the instance

12212.001 -> on which the add numbers was called on the same instance,

12216.3 -> whatever the value of instance variable is just print

12219.9 -> that thing out.

12220.9 -> So this is implicitly put in here you

12223.2 -> need not use this keyword.

12225.1 -> This keyword is usually used

12227.2 -> when you have something like this right when you

12230.7 -> have instance variable suppose.

12233.6 -> You have something of this sort.

12235.2 -> Right?

12235.8 -> One of your parameters is same as

12238.2 -> as the instance variable, right?

12240.3 -> So you want to differentiate which is the instance variable

12243.8 -> and which is this variable right?

12246.2 -> So that's when you

12247.8 -> use this When you say this dot instance variable,

12252 -> this is referring to this instance variable

12254.1 -> and this instance variable

12255.7 -> to the right hand side is referring to this one.

12259 -> Alright, so that's

12260.4 -> when you have to explicitly put this or in other cases.

12264.746 -> It's done by the jvm itself.

12266.9 -> You did not take care of it.

12269.7 -> All right, so So,

12272.6 -> this can be passed as an argument

12274.942 -> in the Constructor call.

12276.9 -> This can be used to invoke current class method.

12280.453 -> This can be passed as an argument the method call

12284.4 -> and this can be used to invoke current class Constructor.

12289.965 -> This could be past basically if there is one more.

12300.6 -> so say for example,

12302.2 -> you have something of this sort which is pretty big though,

12305.1 -> but Admitted taking calculator as its parameter.

12314.6 -> Okay, so I'm just trying to demo you could actually take

12319.3 -> calculator as an argument for any of the methods within.

12323.9 -> All right.

12325 -> So you have ADD method

12326.75 -> which takes calculator as its parameter.

12330.3 -> Alright, so here say for example within this method don't think

12334.6 -> about the logic it's not logical though.

12336.9 -> I'm just trying to show you it could be done.

12339.5 -> Right?

12340.6 -> So I have ad and I put this within your method

12347 -> you could have you could pass as an argument you could pass

12350.8 -> this as an argument.

12352.11 -> So basically you are invoking this one.

12355.1 -> So now if I print it

12357 -> you can see in add numbers you have this method being called.

12365.5 -> So yeah here you can see printing out

12368.3 -> the add method taking calculator has its parameter.

12372.1 -> So basically it's calling this on by passing this.

12377.1 -> So here we spoke about the Constructor earlier.

12379.891 -> We saw how this could be used in The Constructor and one

12383.204 -> of the use cases

12384.102 -> as I said here you could see that similar to the example

12387.337 -> that I spoke regarding the instance variable.

12389.9 -> You could see the parameter the name

12392.323 -> of the parameter is rule number

12394.342 -> which is same as the name of the instance variable.

12397.6 -> This one is pretty much similar to that.

12399.9 -> You could see that the name of the parameter

12402.8 -> that is passed to the Constructor is same

12405.017 -> as the instance variable name the rule number two.

12408.6 -> The left hand side is nothing but instance variable

12411.6 -> within the class info whereas to the right hand side.

12415.394 -> It's a rule number

12416.5 -> that is passed as an as an argument to the Constructor

12420.2 -> similarly for the name you have this dot name,

12423 -> which is referring to the name the instance variable

12426.2 -> in the class info and to the right hand side.

12428.4 -> It's a parameter that's passed to the Constructor.

12431.752 -> That's a typical use of this.

12434.5 -> So we are creating a message here and you can see

12437.4 -> that we are giving a call within the Constructor.

12440.2 -> This is within the Constructor actually,

12442.438 -> so we saw this in the previous example.

12446.2 -> Basically, this is

12447.41 -> what it does write this value of 0 that is

12450.251 -> what this is doing within the Constructor you have this

12453.861 -> and you are giving a call.

12455.7 -> So in this case this Annie would give a call to message string n

12461.076 -> and would print it out.

12463.5 -> So how does it work the main function is executed.

12467.7 -> So again, this is a sequence in which the things execute

12471.2 -> behind the scenes.

12472.507 -> The main function is executed first,

12475.2 -> when an object of the class is created a default Constructor

12478.7 -> is called okay,

12479.723 -> in this case, the one without parameter is called

12483 -> right then you have this dot any

12485.5 -> which is nothing but you're giving a call

12488 -> to the Constructor within the same class,

12490.6 -> but with the parameter any so the jvm would check

12494.4 -> whether you have a Constructor with parameters as string,

12498.6 -> so it finds it and it would give a call to that Constructor,

12502.868 -> which is nothing but the Constructor

12505.4 -> that you see here in a Blue Block right,

12509 -> then it would similar to any method

12511.8 -> after the method invocation is done.

12514.027 -> It comes back to the calling method, right?

12516.7 -> So after this and is called it comes back here then it prints.

12521.067 -> Welcome to edu Rica.

12522.8 -> And once this is done,

12524.4 -> it would go back to the main method in general.

12527.5 -> What happens is whenever a method is invoked

12530.066 -> the local variables

12531.274 -> and everything is pushed

12532.8 -> onto the stack similar to C. Write in C.

12535.343 -> Also you have a calling stack.

12537.3 -> So your local variables go into the stack.

12540.114 -> The calling method is invoked

12542.111 -> after the method is being invoked

12544.199 -> and is completely done.

12545.7 -> It would come back to the stack

12547.5 -> and start off from where it had left earlier.

12550.8 -> So typically how the subroutines

12552.4 -> and everything work in programming language.

12554.7 -> That's how it's done in Java as well.

12556.9 -> So that's why we have calling stack.

12560 -> So that's the sequence of execution that happens.

12563.8 -> So let's start off

12564.989 -> with object-oriented programming Concepts.

12567.8 -> This is pretty much generic.

12569.574 -> This is not something that is just for Java.

12572.3 -> So this is object oriented programming concept,

12575.4 -> which usually all

12576.4 -> the object-oriented programming languages use it

12579.9 -> or adhere to it.

12581.453 -> So we have Which we'll be covering up in the topics

12585.3 -> to come polymorphism,

12587.3 -> which is we have like static polymorphism

12590.2 -> and we have Dynamic polymorphism cover it up in details.

12594.4 -> The coming slides

12595.7 -> will talk about what is abstraction and also

12598.504 -> how Java has encapsulation

12600.2 -> or how Java is aligned words the encapsulation feature

12603.48 -> of object-oriented programming.

12605.4 -> So let's start off with inheritance just to give

12608.7 -> you an analogy you could think of inheritance anything

12611.9 -> that is derived have some super class

12614.5 -> or you have something from which other subclasses are derived

12618.6 -> when you have some feature of your parents.

12621.202 -> We say that you inherited right

12623.109 -> because you have got it from your parent.

12625.462 -> So you have a parent

12626.615 -> so this could be an illogical to something of that sort.

12629.8 -> Maybe you are looks is inherited from your parents sort

12633.1 -> of that is exactly what inheritance is all about.

12636.4 -> You have a parent class

12637.997 -> and you could have subclasses out of it

12640.576 -> and this subclass is would inherit.

12642.922 -> Features or inherited State or the behavior?

12645.891 -> I would say of your parent class.

12648.085 -> So to give you an example

12649.8 -> as you could think of vehicle right vehicle is generic thing

12653.8 -> which could be a super class

12655.3 -> so vehicle could be thought of as a superclass.

12658.462 -> Now, there are subclasses to Vehicles you have bike

12661.9 -> which is a type of vehicle you have car

12664.5 -> which is a type of vehicle you have buses,

12667.2 -> which is again a variant of vehicle and truck

12669.912 -> of course is again a vehicle.

12671.7 -> So basically this defines easier relationship by

12675.2 -> if you read it out you could Clearly say

12677.4 -> that bike is a vehicle car is a vehicle

12679.715 -> but it's a vehicle and similarly truck is vehicle.

12683.102 -> So basically this is something like it defines.

12686 -> He's a relationship.

12687.568 -> So let's see about how actually this classes

12690.9 -> or the sub classes inherit

12692.501 -> from the parent classes just to read out inheritance

12695.746 -> is a powerful feature object-oriented programming

12698.8 -> through which one object acquires some

12701.625 -> or all properties.

12703.006 -> Behavior of parent object.

12705.3 -> So as I said, it's an easy relationship.

12708.3 -> So he's a relationship is represented in Java

12711.22 -> through inheritance.

12712.604 -> It could also be seen as a parent child relationship.

12716.2 -> So subclasses are actually child of parent classes

12720.8 -> in the previous case you have by which is a subclass

12724.9 -> of superclass vehicle.

12726.8 -> So vehicle is a superclass

12728.438 -> and henceforth we would be talking in this terms

12731.48 -> of we would be using this terminology is so

12734.2 -> just wanted to be sure you get it so vehicle is nothing

12737.73 -> but a superclass

12738.84 -> and by could be henceforth referred

12741.2 -> as subclass child classes would be referred as subclass.

12745.3 -> So you have method overriding

12747.3 -> what do you achieve by inheritance is more

12750 -> about method overriding to achieve runtime polymorphism.

12753.922 -> And the second thing is code reuse ability

12756.867 -> as I mentioned the subclass would inherit

12759.644 -> properties and behavior from your superclass.

12762.7 -> Your parent class so there could be some method defined

12766.2 -> in your super class

12767.7 -> which need not be redefined in your subclass.

12770.7 -> It inherits by itself.

12772.3 -> That is the property of inheritance.

12774.2 -> If it has got a common Behavior like say you have two kinds

12777.3 -> of calculator different types

12778.75 -> of calculated the example that we spoke about yesterday.

12781.5 -> There could be a parent class calculator,

12783.5 -> which is adding numbers as is you provide two numbers.

12786.9 -> It adds up and it gives you maybe this add

12789.718 -> Behavior could be added

12791.3 -> into the calculator Claus now Suppose there is

12794.299 -> a subclass of calculator

12795.7 -> where in you

12796.5 -> have this scientific calculator or something

12799.049 -> which is modifying this behavior of our

12801.3 -> which is using the same behavior

12802.9 -> of add right basically a normal calculator

12805.6 -> or a scientific calculator will have the same add

12808.1 -> Behavior adding up two numbers.

12810 -> Whatever you send it as a parameter,

12812.181 -> it would add it up and give you the result.

12814.8 -> So basically you would Define this ad in the calculator

12818.2 -> in the scientific calculator.

12819.905 -> That would be the subclass

12821.3 -> of your calculator you need Redefine this add method.

12824.558 -> It would inherit from the calculator method.

12827.2 -> So that reduces would redundancy

12829.407 -> or it helps you in code reuse ability.

12831.9 -> You need not redefine the add method we have lot

12835 -> of slides to come about method overriding

12837.521 -> and Method overloading

12838.908 -> so I won't talk it right away.

12840.8 -> This is inheritance.

12842.243 -> You have a manager class and you have like employee

12845.937 -> which is extending manager.

12847.806 -> So what we are trying to show here is e dot salary

12851.2 -> as you could see here.

12852.494 -> There's a salary property in a manager and this employed

12855.8 -> to is extending manager

12857.472 -> and we could see here

12858.989 -> that employee to in Harrods salary property though.

12862.6 -> It doesn't have a salary property.

12864.453 -> We are able to access the salary property

12866.7 -> from employee to let me give you an example.

12870.2 -> You just have to click on create new project

12872.999 -> and give some project name.

12874.845 -> I'll give a dude

12875.927 -> a car modules 3 so it opens up a new window you could go

12879.5 -> to the source folder

12880.8 -> and you could right click on it and Create a new class.

12884.076 -> So basically I'll do one thing.

12885.835 -> I'll create an employee class.

12887.622 -> I'll follow the same example that's been mentioned here.

12890.9 -> I create calm down at Eureka dot manager class.

12895.1 -> So calm down Eureka is nothing but the package name

12898.2 -> and manager is your class name.

12900.5 -> So now I Define a property here say salary in that case,

12904.6 -> right suppose.

12905.8 -> I say maybe I will put it as wrong salary.

12909.3 -> So I Define a property within your manager,

12912 -> which is salary.

12913.2 -> Now I Define one more class.

12915.5 -> So you could either Define it with in the same file

12918 -> or you could create a new class for Simplicity.

12920.7 -> I create a new class.

12922.1 -> It will create employee.

12924.3 -> So it created an employee class within calm down Eureka package.

12928.9 -> Now, let's do main

12931.1 -> which is your entry point for the program.

12933.7 -> Now as you could see I haven't defined

12936.5 -> salary within employ.

12938.6 -> The first thing that I'll have to do is we

12941.082 -> are talking about inheritance.

12942.9 -> So employ extends.

12944.938 -> This is a keyword used for inheritance.

12947.962 -> So employ extends manager.

12950.1 -> So now you could see there is a property

12952.4 -> which is salary

12953.276 -> which is defined in the manager and this employee

12956.2 -> which is the subclass of manager and let's see

12959.2 -> if salary is accessible to employ.

12962.1 -> This is a place of manager.

12964.1 -> So I Define employ EMP is equal to Nu employ.

12967.7 -> This is how we create instance of the class using new now.

12972 -> Let's see if just for Simplicity.

12974.6 -> I will give this e MP dot salary you could see that right just

12979.5 -> to be sure I print out so

12981.5 -> as we can see here salary though.

12984.3 -> It's not defined in employ.

12986.5 -> It has been inherited from rather from your manager.

12990.131 -> We can have one more instance created

12992.606 -> which is like manager is equal to new manager.

12995.7 -> This is instance of manager class.

12997.9 -> Now, I do manager dot salary is equal to salary of manager.

13003.1 -> Is it just printing it out?

13005.6 -> So what we have done here is again,

13008 -> I repeat the same thing.

13009.2 -> So we have a manager within manager.

13011.588 -> We have defined a field salary and we have employee

13015.1 -> which is extending manager and the employee class.

13018.498 -> We don't have the field

13020 -> or we don't have the property salary defined here,

13023.111 -> but we could see here

13024.4 -> in this example wherein we created the instance of employ

13027.8 -> and we are accessing salary property from here though.

13030.917 -> It's not defined specifically in employee.

13033.287 -> It's been inherited from the parent class

13035.6 -> that's manager and manager of course has salary field

13038.8 -> which is been access of here

13040.2 -> and we could assign some value to it.

13042.3 -> I run the program it should compile

13044.447 -> and create a class file

13045.9 -> out of it and it runs the class file using jvm.

13048.9 -> So yeah, as you could see here,

13050.785 -> it's printing out values for salary of employee

13053.593 -> and manager as well.

13054.834 -> So that's about inheritance it see inheriting

13057.455 -> the property salary from parent loss.

13059.6 -> Now, what are different types of inheritance

13061.7 -> that we have this Bill inheritance wherein you

13064.507 -> have a parent class

13065.751 -> and you define a subclass out of it so similar

13068.7 -> to what we spoke.

13070.007 -> We had a manager class and we had employee class

13073.6 -> which was inheriting manager.

13075.549 -> That's about single inheritance.

13077.7 -> You can have hierarchical inheritance wherein you

13080.976 -> could have multiple classes inheriting from a same class.

13084.8 -> So you could have a

13086.123 -> and be inheriting from a single class.

13088.7 -> You could have multi-level inheritance wherein you

13091.4 -> have one class inheriting from another and again,

13094.357 -> you could have subclass of the subclass parent class

13097.5 -> you inherited or you subclass it or extended whatever you say

13101.378 -> so there is one level.

13102.8 -> So you have a child class.

13104.45 -> Now, you could have one more sub class

13106.8 -> of this child class.

13108.2 -> That's what multi-level inheritance is all about.

13111 -> So as we go through the example,

13112.618 -> it should give you a clear idea about what I'm talking

13115.3 -> about so single inheritance,

13117.461 -> so we have vehicle and we have bike

13120.2 -> which is extending vehicle.

13121.991 -> So this Similar to what we defined here.

13124.605 -> So what we did here is single inheritance.

13127.347 -> You had a manager and you subclass debt

13129.889 -> and this is just single inheritance one level.

13132.9 -> So what is hierarchical inheritance?

13135.7 -> So you have a vehicle

13137.3 -> and you have two subclasses created out of vehicle.

13140.941 -> So there are two child's of a parent class.

13144 -> So this could be pretty much similar

13145.9 -> to a parent having two kids right there could be two cats

13149.194 -> and they inherit some property from your parent.

13151.958 -> So it's pretty much similar to that.

13154.053 -> So you have a vehicle class

13155.735 -> which is the super class and you have subclasses to it.

13159.2 -> So, let's see how this works.

13161.204 -> So I create a vehicle class which is the super class.

13164.798 -> I have a vehicle class

13166.399 -> and civically class has a property

13168.8 -> which says integer say number of Wheels.

13171.9 -> This could be one of the property of a vehicle class.

13174.9 -> You have say for example, you have the mileage.

13178.6 -> So these are common properties that you have in vehicle.

13181.6 -> Say you have Motion just to add a behavior

13184.8 -> to this particular class.

13186.4 -> I Define method move

13187.757 -> and I just print this thing out here.

13190.2 -> I defend two properties here for vehicle class,

13192.986 -> which is number of wheels

13194.5 -> and the mileage and add a behavior to the class

13197.589 -> by introducing method

13199 -> which is move which is nothing but I'm just printing it out.

13202.7 -> So ideally you would have some functionality written

13205.35 -> within or you would have lines of code written within just

13208.426 -> because we are talking about inheritance just

13210.8 -> to show the properties

13212.011 -> and behavior is been inherited by the subclass

13214.529 -> for Simplicity sake we

13215.761 -> don't have any logic written within move.

13217.8 -> It's just printing it out saying

13219.4 -> that just to indicate that you know,

13221.3 -> there's a move method within the vehicle class

13223.947 -> is being called.

13224.774 -> We're just printing it out there but in reality

13227.2 -> as I said there would be actual logic written with them.

13230.1 -> So now I Define car class and I defined by class.

13234.6 -> So now I say

13235.8 -> that car is extending which is nothing

13238.604 -> but sub class of vehicle.

13240.5 -> So remember we said easy relationship.

13242.8 -> Chip car is a vehicle.

13244.3 -> So what we are saying is subclassing

13247.1 -> or we are inheriting properties of vehicle into car suppose.

13251.7 -> I change the property

13253.4 -> of any you method within or say I can have its own moment

13257.8 -> when car cross.

13259.5 -> So basically we are overriding it.

13261.7 -> What we are trying to do is we are trying

13263.7 -> to whatever method you had within your car class

13267.6 -> or the vehicle class.

13269.105 -> You are overriding it for the car class.

13271.908 -> You are trying to change something similarly

13274.912 -> in your by class.

13276.1 -> You could overwrite the move.

13278.055 -> So first thing

13279 -> that we'll have to do is bike should extent your vehicle.

13283.032 -> So bike is a vehicle we are extending it now.

13286.2 -> We are again overriding this move method to say

13290.4 -> move in by class.

13292.3 -> So now basically we can have seven more just

13295.316 -> for simplicity's sake we have just a class wherein you

13299.138 -> would write the main method.

13301.041 -> So this is generally

13302.4 -> Practice were in such classes are called as client classes

13306 -> where in you have a main method and you do something with it?

13309.6 -> I just call it as automobile management class.

13313.1 -> So you have a main method so suppose you want

13316.29 -> to change the number of wheels for a car.

13319.1 -> So what you would do is car car is equal to Nu

13322.46 -> or it won't be carved would be

13324.7 -> like suppose I put Mercedes is equal to new car

13329.169 -> by create Mercedes.

13330.7 -> I create BMW is equal to new car.

13333.9 -> So now what we do is I want to overwrite the property

13337.5 -> that is number of wheels for Mercedes to for similarly.

13341.449 -> I could have a bike class say r 1 is equal to Mu

13344.8 -> by something of this sort you could have Ducati is equal

13348.518 -> to Nu by so this is just to give you an idea of

13351.625 -> how we have classes and objects right now.

13354.443 -> You could imagine what objects is all about.

13357.4 -> So Mercedes is object of car BMW is object of car.

13363 -> Arvin is object of bike

13364.8 -> and Ducati is again an object of by so now I could overwrite

13369.4 -> the properties here say number of vehicles

13372.426 -> as to so yeah,

13373.459 -> this is what it is all about.

13375.6 -> This should give you some idea

13377.1 -> about how we use Java you have a class you have subclasses,

13381.6 -> then you kind of create objects

13383.8 -> and you could override the properties with them

13386.8 -> and you could change

13388.2 -> when I say override is nothing but you could modify

13391.3 -> the values within your subclasses and similarly,

13395 -> you could change the behavior vehicle

13397.1 -> by itself would have some Behavior defined

13399.8 -> but Mercedes and BMW,

13401.308 -> which is a car would have its own kind of behavior,

13404.9 -> which is not inherited from parent

13407 -> you're overriding it when you say

13409.347 -> this this could be an illogical to something

13412.1 -> like kid kid doesn't have the same features as a parent.

13416.6 -> It is something like it's been overridden right?

13419.1 -> It's peculiar to that particular kid,

13421.3 -> and that's what this is.

13422.696 -> About so you could override it.

13424.5 -> Now.

13424.7 -> Let me print move or let me call the move method on BMW

13429.1 -> so you could see a move method

13431.5 -> and when I run it it should show move method in car class

13436.3 -> since it's a movement

13437.7 -> that called on car BMW is instance of car.

13440.8 -> So this should give you some idea about

13443 -> how are we inheriting properties and behavior from parent class.

13446.9 -> So here we can see that move in car class.

13449.726 -> So again, you could Define your own method

13452.552 -> within your subclass,

13453.8 -> which is not something

13454.9 -> that is inherited from your parent class.

13457.1 -> So BMW by itself

13458.915 -> or car by itself could have something like sector board

13463.2 -> which is not in vehicle.

13464.4 -> Maybe this is specific to car.

13467.238 -> So this is what we spoke about is hierarchical inheritance.

13471.7 -> Now, let's talk about multi-level inheritance.

13474.8 -> So basically it's nothing but say you have

13477.519 -> a super class category.

13479.039 -> So let me use the same example.

13481.088 -> You have a vehicle class you Have a car

13483.6 -> which is extending vehicle.

13485.676 -> Now I Define one more class,

13487.83 -> which is nothing but superclass Supercar

13491 -> which is extending car.

13493.3 -> Basically, I can put this turbo in Supercar rather

13496.459 -> that would make more sense.

13498.2 -> This is like kind of multi-level.

13500.585 -> So I am putting this turbo here in supercars.

13503.8 -> You have a vehicle class you have a car

13506.5 -> which is surplus of vehicle.

13508.4 -> You have a Supercar which is a subclass of car.

13511.708 -> So all the properties

13513.254 -> that you have in vehicle class could be accessed

13516.586 -> in car as well as Supercar.

13518.5 -> That's what we want to see here.

13520.3 -> So you could have something like say change Wheels

13524.305 -> which is void which is not returning anything here.

13526.9 -> I just want to show you

13528.443 -> that we can still access number of Wheels here though.

13532 -> It's not defined in car or Supercar

13534.6 -> but in vehicle class

13536.004 -> you could actually it is still visible here

13538.951 -> and you can modify it.

13540.421 -> That's the beauty of it again.

13542.415 -> Brief, you have a vehicle class you have a car class,

13545.888 -> which is extending vehicle class.

13548.026 -> You have a Supercar class, which is extending car class.

13551.7 -> So basically there is a multi-level

13553.7 -> of inheritance and all the properties and behavior

13557.089 -> that you have in vehicle class would be visible to car class

13561.2 -> as well as Supercar cross

13563.1 -> and Supercar class can access properties and behavior

13567.6 -> that is there specific to car class.

13570.1 -> What I'm trying to say is if you define a new method here,

13573.6 -> so I just mention here Behavior specific to class to car.

13578.9 -> So there's some behavior that is specific to car

13582.051 -> that we have defined within the car class.

13584.9 -> Now Supercar class can access this one as well.

13588.9 -> So you could see here you could access Behavior

13591.66 -> specific to car as well.

13593.1 -> If you look it as a tree.

13594.6 -> This is a leaf node.

13596 -> This is super car class can access everything

13599.384 -> from vehicle and car class.

13601.7 -> Whereas.

13602.3 -> Our class can access everything from vehicle class,

13605.8 -> but it's not the other way around car cannot access

13608.9 -> something that is specific to Supercar.

13611.445 -> There's a turbo method

13612.919 -> that we have put in into the Supercar class.

13615.8 -> Now.

13616 -> If you try to access Turbo from here,

13619.1 -> you won't be able to access it.

13620.6 -> All right, so it's not the other way round.

13622.8 -> So you cannot access something

13624.3 -> that is specific to your subclass

13626.7 -> in your super class.

13627.8 -> Whereas you can access anything

13629.84 -> that is there in your superclass into your subclass.

13633.2 -> So it's a one directional flow from superclass to subclass.

13637.1 -> Now, let's talk about has a relationship has

13639.629 -> a relationship is nothing

13641.005 -> but you have properties within your class,

13643.417 -> which is has a relationship.

13645.031 -> All right.

13645.599 -> So say for example employee, right?

13647.65 -> We defined the employee class

13649.4 -> and employee would have an ID specific to employ

13652.7 -> and it can have salary and stuff like that

13655.3 -> which is has a relationship

13656.9 -> which is nothing but employ as ID sort of right so a department

13661.476 -> in a class Let's talk

13663.032 -> about this example a department in a college

13666.433 -> has several professors without existence of departments.

13670.4 -> There is good chance

13671.752 -> for the professor's to exist hence professors and Department

13675.852 -> are loosely associated.

13677.447 -> And this loose Association is known as aggregation.

13680.962 -> So one can exist without other which is loose Association

13684.901 -> and such thing is nothing but aggregation.

13688.2 -> So here you could see employ here.

13690.8 -> You could see name name class itself,

13693.356 -> which has got first and last name.

13695.7 -> So basically you have a name class

13697.641 -> which has got property as first

13699.532 -> and last and which is nothing but the first name

13702.4 -> and the last name of any entity.

13704.464 -> It's not associated with anything right now.

13707.332 -> It's a different entity name is a different entity

13710.6 -> which would have first and last name now

13713.7 -> this employee info class,

13715.577 -> which has got ID and which has got name

13718.5 -> so you can see name hear this name property is nothing

13722.3 -> but The instance of name class

13724.6 -> that is there the left hand side.

13726.6 -> So this is has a relationship.

13728.9 -> This says that employee info has name.

13731.9 -> So basically this is what it is

13733.905 -> when you talk about has a relationship its containment.

13737.4 -> Basically you have class as a property in a class.

13741.2 -> So in this case name is a property

13743.703 -> within your employee info

13745.6 -> and similarly this name could be used somewhere else as well.

13749.3 -> It's not that it has to be used just in employee info.

13752.5 -> That's a kind of Detachment they have right.

13754.9 -> It's not tightly coupled.

13756.536 -> It's Loosely coupled or decoupled.

13758.585 -> So basically you have name

13760.2 -> which is altogether a different entity defined as a class

13763.088 -> which would have first and the last name

13765.1 -> and you would have an employee in for which is containing name

13768.6 -> which has name.

13770 -> So this is has a relationship

13771.8 -> and also to give you idea about has a relationship.

13774.9 -> It's not just it has to be object.

13777.1 -> Right so vehicle has number of Wheels vehicle has Uh,

13783 -> this could be thought of as a relationship.

13785.47 -> So let's talk about polymorphism.

13787.3 -> Now when one task is performed by different ways,

13791.053 -> then it is called as polymorphism Polly is multiple

13794.899 -> of ism is forms.

13796.1 -> Basically, that's the meaning behind it.

13798.4 -> So multiple forms.

13799.9 -> That's what polymorphism means

13802.092 -> and when one task is performed by different ways,

13805.6 -> then it's called as polymorphism this person

13808.509 -> which is the super class.

13810.2 -> You have a subclass student is again person millionaire is

13814.812 -> a person these are super classes.

13817.3 -> So you have a person class you have super class student

13820 -> and millionaire you have a behavior,

13822.058 -> which is nothing but P Bill

13823.607 -> and which would be specific to both of them.

13826.075 -> So as we move on you would get much more idea

13828.6 -> about the different kinds,

13829.9 -> but basically you have multiple forms.

13832.1 -> That's what polymorphism is all about.

13834.3 -> So, what is Method overloading so we spoke about this yesterday

13838.5 -> if you remember we spoke

13839.977 -> about Constructor overloading we're in you

13842.5 -> Had multiple Constructors Define one was integer integer,

13846.6 -> and the other one was

13847.842 -> like it was taking three parameters integer integer

13850.783 -> n 3 integers, right?

13852.025 -> So basically this is what method overloading is all about to have

13856 -> the same name of a method

13857.622 -> but you have different number of parameters passed to the method

13861.57 -> or you have different type

13863.2 -> of parameters passed to the object to the method

13865.964 -> and based on that.

13867.034 -> It would understand which is a method

13869.2 -> that needs to be called.

13870.741 -> So suppose you have ad with two integer parameters Define

13874.334 -> and you have ADD with three integer parameters defined now

13878.06 -> when you invoke add method on a particular instance

13881.319 -> of calculator and you pass two parameters to it,

13884.293 -> it would appropriately call add method with two parameters

13888 -> and if you pass three parameters to it,

13890.326 -> it would call one with three parameters

13892.653 -> or it would resolve it

13894 -> during the runtime which one to be called rather.

13896.4 -> It's not overloading doesn't happen during runtime.

13898.9 -> It's done during the linking of the resolving operation.

13902.5 -> Ben's during the compile time itself.

13904.937 -> That's why it's static polymorphism method

13907.6 -> overloading is nothing but static polymorphism.

13910.184 -> So return type is not taken into consideration when it comes

13913.5 -> to Method overloading.

13915.1 -> It's just the parameters that a particular method takes.

13918.986 -> So Alex wants to write a code

13921.111 -> which can be used to find out the area of triangle

13924.7 -> as well as of circle.

13926.4 -> So generic code which would have area of triangle

13929.9 -> and circle so such are the instances wherein you

13933.1 -> could use method overloading.

13935.116 -> So what's the thought behind is I want to find area

13938.533 -> of both the shapes here area is the common method.

13941.924 -> It's there for both the shapes.

13943.959 -> It's therefore rectangle.

13945.6 -> It would be there for square.

13947.2 -> It would be there for Circle and so on and so forth.

13950.441 -> So basically you would have a shift method

13952.936 -> which would have area which is a common method.

13955.829 -> So instead of writing two methods of different names.

13959.1 -> I will write area as the method name for both shape.

13962.4 -> And a path different

13963.758 -> arguments according to the respective shape.

13966.579 -> So instead of defining multiple area methods

13969.5 -> you would have just a general area method defined

13972.3 -> in your shape class

13973.6 -> and your subclasses would overloaded as

13976.45 -> per the type of shape.

13978.1 -> So here we can see that this area class there's area method

13982.54 -> which is taking integer

13984.3 -> since it's a triangle its base and height.

13987 -> So it's taking base and height as parameter.

13990.1 -> So Java doesn't understand base and height.

13992.457 -> This is user defined by the way.

13994.34 -> It understand.

13995.089 -> There are two integer parameters passed through the area Whenever

13998.54 -> there are two integer parameters passed to area method.

14001.52 -> This one would be called.

14002.9 -> The other one is again,

14004.4 -> we have one more method

14005.9 -> which is area which is by the same name

14008.711 -> and which is taking just one integer parameter,

14012.115 -> which is radius.

14013.3 -> So this is supposedly for circle Pi R square.

14016.7 -> So during runtime when you call it,

14018.7 -> so I'm not repeating this exercise again,

14021.052 -> because we did the same.

14022.4 -> Yesterday if you remember we

14024.118 -> kind of had multiple add methods in the calculator and we saw

14027.8 -> that it was getting resolved to the proper one

14030.447 -> based on the number of actual parameters

14032.7 -> that you pass.

14033.4 -> So I will just read

14034.7 -> through the slides to make you give more explanation on this

14038.201 -> but it's pretty straightforward.

14040.1 -> So here you have area method which is ticking for six

14043.9 -> which is nothing but it would get resolved

14046.8 -> during compile-time

14047.805 -> this particular area method invocation would get resolved

14051.276 -> to this one

14051.937 -> since it is taking two integer parameters.

14054.482 -> Second one is taking just one integer parameter,

14057.4 -> which is 5 so it understands

14059.1 -> that it has to call this area method

14061.2 -> the second area method that's been defined

14063.458 -> in method demo and it would call it accordingly.

14065.824 -> So here you could see

14067.1 -> that when you run this particular program you could see

14069.8 -> that the first one resolved it to Triangle and it said

14073.5 -> that the area of triangle is nothing but 4 into 6

14076.921 -> into point five,

14078.078 -> which is nothing but 12 the second one

14080.718 -> goes 2 pie R square.

14082.116 -> And it gives answer as seventy eight point five.

14085.4 -> So you could see there are two different invocations

14088.252 -> done based on the number of actual parameters.

14090.907 -> Now, let's talk about type of parameter the method

14093.8 -> overloading can happen on type of parameter as well.

14096.906 -> So you could have multiple methods with the same name

14100.097 -> taking same number of arguments

14102 -> but different data types

14103.418 -> one could be taking integer as a parameter.

14105.9 -> The other one could be taken string as a parameter

14108.7 -> and during runtime ordering compile time itself.

14111.8 -> It would resolve that, you know,

14113.498 -> this one should be resolved to this invocation

14115.887 -> and the other one should be resolved to the other one.

14118.7 -> So basically it tries to resolve based on the parameter based

14122.547 -> on the data type of the parameter

14124.6 -> that you pass.

14125.5 -> So here's the example wherein you have two different methods.

14129.796 -> I will take this one.

14131.3 -> Say for example, I Define public integer.

14134.911 -> So it's a dummy value to be printed one

14138 -> of the best practices

14139.6 -> when you write Java code is to express it, right.

14142.4 -> So you can have a big variable name you

14144.6 -> shouldn't be restricting on variable name

14146.688 -> which makes it difficult

14148.099 -> for other programmers to understand.

14150.1 -> So it's good to have big variable name versus small one,

14153.635 -> which is not that expressive.

14155.5 -> So here I said dummies string value to be printed.

14159.8 -> I'm printing integer value is nothing but dumb integer value

14163.7 -> and here I am printing

14165.2 -> so we have two methods with the same name

14167.284 -> but it's taking different data types as argument

14169.8 -> and we are just printing it out.

14171.6 -> So I Define a main method here and I Define manager.

14175.8 -> So we have instance of manager senior manager grade

14179.1 -> 2 dot display I pass integer to it.

14182.8 -> I pass hundred to it and I pass

14186.1 -> so I have to Method invocations here.

14188.217 -> One is first one.

14189.244 -> We are passing hundred the second one.

14191.358 -> We are passing a string to it and it gets resolved.

14194.41 -> You could see

14195.142 -> that the first one would go to this display method

14197.9 -> which says printing integer value the next one

14200.8 -> would go to this.

14202 -> Display method which print string value

14204.6 -> so you could see here.

14205.847 -> Right?

14206.2 -> So first one is printing integer value.

14208.277 -> The second one is printing string van.

14210.3 -> So based on the type of the parameter

14212.176 -> that you pass through are passed to the method particular method

14215.5 -> would be called This is static polymorphism.

14217.9 -> Now what's runtime polymorphism.

14219.8 -> So since it is resolved during the compile time,

14222.6 -> it is static polymorphism.

14224.2 -> There are few things

14225.2 -> that gets resolved during the runtime

14227.5 -> or the compiler cannot judge it up front what the instance

14231.2 -> would be and that's

14232.355 -> when it does it during the runtime

14234.328 -> and that is nothing but dynamic polymorphism

14236.9 -> or method overriding so method overriding is mostly used

14240.5 -> in an easy relationship.

14242.3 -> So in one of the methods or we saw in vehicle and car example,

14247.453 -> we have a move method here and here we overrode it.

14251.4 -> You can see override annotation here for the move

14254.7 -> because you're overriding it overriding the behavior

14258 -> of vehicle in car class.

14259.753 -> So that's where it says

14261.454 -> that this Easy relationship method overriding must be used

14265.751 -> in case of inheritance

14267.323 -> that is easy relationship method must have the same name as

14271.47 -> in the parent class.

14272.894 -> We saw in the move in the example move.

14275.631 -> We have the same name as in this super class.

14278.8 -> So huichol has a method move and car has a method move

14282.838 -> as well method must have the same parameters as

14286.3 -> in the parent class as against method overloading

14289.8 -> which has different parameters method overriding

14292.9 -> you have to be sure

14294.166 -> that it takes the same parameter if I change this to integer

14298.3 -> if I add an integer parameter to it,

14300.7 -> so it's not taking it as overriding you could see it.

14304 -> It's not been taken as

14305.347 -> overriding because you have integer parameter to it.

14308.5 -> So basically it has to have same number

14311 -> of or it has to have the same signature as your parent class.

14315.4 -> So that's about method overriding.

14317.8 -> Let's have a demo on this so which we already saw

14321.069 -> but I will again A trait on that

14323.257 -> so basically this example you could see there's a man class

14327.084 -> which has got a pay method

14328.875 -> which is adding Behavior to the man method

14331.7 -> and you could see it's a dummy printer

14334.7 -> and you have a millionaire is a man and you could see

14339 -> it overrides the pay behavior

14341.5 -> and you run this program.

14343.268 -> One thing to note here is you can assign me linear to man.

14347.229 -> You can assign unlike all the examples

14349.8 -> that we saw we are creating instances of the same class

14353.2 -> or assigning the instance of a class to the same class.

14356.7 -> But in this case you could see the instance

14359.1 -> of millionaire is being assigned to reference of man.

14362.5 -> This is something

14363.6 -> that happens only in Easy relationship or inheritance.

14367.49 -> So what I am trying to say here is a go-to

14370.5 -> automobile management I have car

14373 -> I have a new car

14374.155 -> which is Mercedes I could assign this Mercedes to vehicle

14378.2 -> since Mercedes is a vertical it

14379.6 -> should be a sign you should be able to assign it.

14382 -> This is something

14383.213 -> that you need to keep in mind your subclass object

14386.835 -> could be assigned to superclass.

14389.123 -> So here we have Mercedes being assigned to vehicle.

14392.7 -> But one thing to note here again is the tricky part is

14396.3 -> vehicle itself has its own move method, which

14400.2 -> Moving vehicle class

14402.1 -> and Mercedes which is car itself has its move method

14407.046 -> with this move in car class.

14409.2 -> So the tricky part here is

14410.977 -> when you would do something like vehicle dot move just

14414.6 -> give a thought about it which one should be called.

14417.631 -> So you have two variants of move method here.

14420.3 -> You have one in car and one in vehicle.

14423.4 -> So the one in vehicle is printing out moving

14426.4 -> vehicle class and one

14427.9 -> in car is the overridden version

14430.5 -> of vehicle with says move in car class.

14433.8 -> Now, what we are doing here is we are creating

14436.905 -> an instance of a car class

14438.7 -> and we are assigning that instance to vehicle

14441.9 -> and we are calling the move method.

14443.9 -> So just give a thought

14445.016 -> whether the move method on the vehicle class

14447.2 -> would be called or a move method

14448.959 -> on the car class would be called.

14450.895 -> So this is

14451.5 -> where method overriding comes into picture so method

14454.784 -> overriding is nothing but it's a runtime polymorphism

14458.132 -> which is done at the runtime.

14460 -> So during the runtime jvm would see

14462 -> that Mercedes is nothing but the instance of car though,

14466 -> it's assigned to vehicle

14467.419 -> which is super class still an instance of class.

14470.2 -> So during compile-time jvm wouldn't have a friend knowledge

14473.611 -> that which move are you calling?

14475.476 -> Is it on vehicle class or is it on something else

14478.3 -> or some sub class of vehicle?

14480.1 -> So it doesn't decided during the compile time it delays it

14484.4 -> or there's a lazy binding

14486.103 -> that happens delays it till the time you run it.

14489.2 -> So when you run it,

14490.48 -> it understands that this vehicle is actually pointing to car.

14494.364 -> That's Mercedes.

14495.4 -> So when you run this you could see

14497.379 -> that I will comment out this piece of code.

14499.9 -> So this is how we comment out that's a block comment.

14502.5 -> So when I move this you could see

14504.58 -> that move glass

14505.529 -> on car has been called and not vehicle that is what is

14508.981 -> if you get this concept,

14510.5 -> you're pretty good in terms of object oriented.

14512.8 -> By the way.

14513.533 -> This is an important Concept in object-oriented Paradigm.

14517.3 -> So you could see here move in car classes.

14520.1 -> Called similarly vehicle

14521.881 -> could have I call it as vehicle one, right?

14525 -> I Define one more vehicle here,

14527.492 -> which is like new vehicle

14529.6 -> and I invoke the method

14531.254 -> on vehicle to so the second variant

14533.7 -> would call the move method in your vehicle class.

14536.9 -> The first one calls

14538.3 -> on the curved glass the second one calls on the baker was

14542.242 -> since its object of vehicle itself.

14544.9 -> So basically you have to see on the right side,

14547.301 -> which is the object

14548.299 -> that's been assigned since its object of vehicle.

14551.2 -> It's vehicle.

14551.977 -> But since this one is object of car,

14554.111 -> that's the reason you have car class being called.

14557.1 -> So we had some discussion on this keyword yesterday.

14561 -> So super keyword is similar to that super keyword is just

14565 -> that it is called on superclass.

14567.7 -> This is called on the same class super is called

14570.702 -> on the immediate subclass

14572.3 -> immediate parent class you could have multi levels, right?

14575.652 -> But this one is calling the immediate parent used

14578.4 -> to refer immediate parent.

14579.745 -> Us instance variable used to invoke parent class method

14583.9 -> and there's one more Super keyword one more form

14587.065 -> in which you could use is to have class Constructor.

14590.5 -> So basically whenever you create a class

14592.848 -> whenever you call a class whenever you call Constructor

14596.1 -> of a class by default jvm

14597.959 -> by itself would give a call to the superclass Constructor,

14602.2 -> which we would be looking at the further slides.

14605.2 -> So here we have vehicle leaven,

14607 -> which is a super class

14608.1 -> which defines string Wheels vehicle moves

14610.744 -> because of wheels so that the string

14613.345 -> that the property of a vehicle you have a truck

14616.43 -> which extends vehicle and then within truck

14619.477 -> you have your overriding the wheels property saying

14622.933 -> that truck has four wheels.

14624.8 -> This is kind of your overriding the property.

14628.1 -> It's not called overriding though

14629.7 -> when it comes to properties.

14631.4 -> But basically you have changing the values

14633.8 -> within your truck class print wheel is nothing but a method

14638.315 -> that's defined in.

14639.7 -> Truck which would bring the number of wheels

14642.3 -> in your truck class and it has got super dot Wheels

14645.7 -> which would print the number of wheels in your

14648.17 -> or print the value of the Veals not number of Wheels value

14651.5 -> of the wheels property within your vehicle class.

14655.046 -> So we will look at this one.

14657.2 -> So we have a vehicle class and we have string Wheels

14660.6 -> which is a property within a vehicle class

14662.851 -> which has some value put in right?

14664.7 -> We have a truck class again,

14666.347 -> which has got wheels and it is overriding the value.

14669.313 -> It is just changing the value

14671 -> as truck has four wheels

14673 -> with interrupt class you have print will method

14676.103 -> which is printing the wheel or the value

14678.66 -> that this particular Wheels property holds

14681.3 -> it would print it first one would be the value

14684.1 -> that this particular truck class would hold and the other one

14687.629 -> that you see here the second print statement,

14690.211 -> which is doing super dot Wheels is actually printing the value

14693.8 -> of wheels in vehicle class.

14696.3 -> So, let me show you a quick demo on this thing.

14699.401 -> So we Have a vehicle class

14701.215 -> which were in we are defining the default number of Wheels as

14705.4 -> for say for example,

14706.937 -> and now we have a bike class,

14709.071 -> which is overriding vehicle class.

14711.5 -> And what we are going to do here is we are going

14714.6 -> to change the value of number of Wheels.

14717.3 -> I have a method to print number of fields,

14720.2 -> which would give suppose I change your number

14723.7 -> of Wheels to say to so here we print number of Wheels first

14728.9 -> and I would have one more print statement

14731.821 -> which would be printing super DOT number of Wheels

14735.389 -> within a by class.

14736.7 -> We have a print number of bills method first.

14739.288 -> We are changing the number of Wheels to 2

14741.8 -> and then we are printing the number of wheels for bike

14745.119 -> and number of wheels on the superclass.

14747.5 -> All right, and by default we have set the number of wheels

14751.053 -> in the vehicle class

14752.3 -> to before so we have a bike class now I remove this

14756.5 -> to so now I print the number of Wheels.

14760.1 -> So I create the instance

14761.8 -> of bike and I invoke print number of Wheels.

14764.6 -> Now you could see

14765.641 -> that first it would print to and on super dot.

14768.4 -> Basically.

14768.988 -> This is what it's going to call so first it

14771.4 -> will print to so basically here

14773.5 -> we need to have one more teacher number of fields

14776.834 -> when it comes to instance variables.

14779.282 -> It's not overridden as such so I have like number

14782.767 -> of Wheels defined here again

14784.799 -> and here I change number

14786.464 -> of Wheels to to so let me run it again.

14789.1 -> So when it comes to instance variable

14791.041 -> when you define one more field here of the same name,

14794.1 -> it's not overriding it.

14795.3 -> It's rather creating a new instance variable.

14798.2 -> So now you could see

14799.2 -> that when you print number of Wheels it's printing out

14802.371 -> to which is nothing

14803.499 -> but the value here value of this instance variable.

14806.468 -> Whereas when you do super DOT number of Wheels,

14809.2 -> you have a default value of 4 here which is been printed out.

14813.2 -> So on super it gives a call to superclass.

14816.6 -> So here you are creating.

14818.229 -> It's at the Constructor level.

14820.2 -> And we can see that so it's more about

14822.9 -> as I mentioned within your Constructor.

14825.4 -> The first thing that is called

14827.2 -> when you create an instance is a super Constructor

14830.362 -> is called first

14831.3 -> and then your sub class Constructor or I mean to say is

14835.2 -> when you create instance of car.

14838 -> So your first thing

14839.3 -> that would be called is the Constructor

14841.2 -> of vehicle and it would do all the initialization

14843.824 -> that's required in vehicle.

14845.3 -> And then it would call the cars Constructor.

14848.908 -> So what I mean to say is for example,

14851.8 -> I create a Constructor here and I print saying

14855.561 -> that we are within Constructor of fecal of superclass vehicle.

14861 -> Now we have this car class and say we have Constructor

14865.707 -> for car class as well.

14867.4 -> Remember we said

14868.4 -> that there's a default Constructor implicit Constructor

14871.1 -> that's already been put by GBM itself.

14873.7 -> You don't have to take care about it.

14875.6 -> So I don't do anything here.

14877.397 -> So basically you need not create you do.

14879.9 -> Right Constructor jvm by default right Constructor,

14882.841 -> unless you want to write

14884.053 -> something or you want to initialize something.

14886.432 -> That's when you would write explicitly you

14888.557 -> would write Constructor.

14889.862 -> But in this case since we are not initializing anything

14892.8 -> as such I won't put a Constructor car.

14895.3 -> What I'm trying to say is we are creating

14897.4 -> an instance of car here.

14898.966 -> And let's see when we create the instance of car.

14902.1 -> There is a super Constructor that's been called.

14904.697 -> That's what I wanted to show.

14906.3 -> So that's why we created a Constructor here for vehicle.

14909.5 -> This is not a method.

14910.627 -> This is constructed by the way,

14912.3 -> since it has got the same name as your class

14914.8 -> and it doesn't have any written value.

14917.284 -> So so I have printed it out saying

14919.5 -> that we are in the Constructor when we call this now

14922.562 -> when we create the instance of car you could see

14925.2 -> that this Constructor of superclass that's vehicle

14928.73 -> that's been called.

14930.053 -> So this is done implicitly by compiler.

14932.7 -> You don't have to care about it.

14934.49 -> So here you could see whenever

14936.255 -> you create the instance of car you would see

14938.526 -> that we are in construction.

14940.173 -> Of superclass vehicle and the second print statement

14943.1 -> that you see is directly for the vehicle sensation.

14946.946 -> So even for car you could see

14949.3 -> so this will get rid of confusion.

14952 -> So there's only one instance of car being created

14954.832 -> and we can see that it is calling vehicle Constructor

14957.891 -> and it's implicitly put

14959.273 -> we don't have to explicitly put it jvm by itself

14962.1 -> operates that way

14963.3 -> and how it calls is nothing but by Super Final keyword we

14967.3 -> again touch based on this one earlier in the session.

14970.6 -> Number one final keyword is non access modifier applicable only

14975.2 -> to variable method or a class when it's applied to a variable.

14979.705 -> We say that the variable content cannot be changed usually use

14983.911 -> final when you want to define a constant

14986.6 -> within your application.

14987.8 -> So that's final a method could be defined as

14990.747 -> final you define a method as final when you say

14993.9 -> that your subclass cannot overwrite it

14996.5 -> that's when you define it as final you define a class.

14999.916 -> As final when you say

15001.284 -> that there cannot be any subclass of that class.

15004.4 -> So you cannot subclass it like

15006.371 -> if you try to extend on a final class you

15009 -> would get an error compile time error saying

15011.2 -> that you cannot extend it.

15012.7 -> So just to show you maybe

15014.2 -> if I make this as final your car would show an error saying

15019.1 -> that you cannot inherit from final class.

15022.029 -> That's Comdata recorded pickle.

15024.273 -> So that's about final class.

15026.3 -> And if you make this method final you

15028.6 -> would again get an error in the class saying

15031.274 -> that you cannot overwrite this the car class you

15034.258 -> are trying to override the move method

15036.688 -> since its final it showing you an error saying that move

15040.3 -> cannot overwrite move in calm dot Ed u--

15043.058 -> recorded vehicle overridden method is final.

15046.1 -> Let's remove this finer

15047.382 -> and you should see the error is gone.

15049.7 -> And also if you want to see at the instance level

15052.86 -> if you define this as for number

15054.878 -> of Wheels as for now within this vehicle,

15057.492 -> if you're trying to modify this number of Units

15060.5 -> to to it would throw you an error saying

15063.131 -> that cannot assign a value to final variable.

15066.1 -> All right, so that's what it does it.

15068.217 -> It's not access modifier,

15069.765 -> but it regulates it in a way

15071.5 -> that you can't change the value in case of variables you

15074.9 -> can change the value in terms of class.

15076.8 -> You can't subclass it

15078.397 -> or you cannot create a child class of a final class

15082.3 -> and in terms of methods,

15084.4 -> if you have final method you cannot override

15087.048 -> that particular method in your subclass.

15089.5 -> So final modifier can be applied to class method instance

15093.1 -> variable class variables local variable and Method parameters.

15097.8 -> So final variable is used

15099.532 -> to create constant variables when it comes to variable

15103.675 -> as I said,

15104.356 -> usually you use final variable

15106.4 -> when you want to have constants, right

15108.576 -> and it would be final static.

15110.4 -> By the way.

15111.2 -> If you have a constant usually final and static

15114.2 -> static final final methods is used to prevent method

15118.2 -> overriding in terms.

15119.7 -> Method the demo that I showed you previously we saw

15123.2 -> that we cannot override it in terms of class.

15126.2 -> When you have a final class,

15127.807 -> you won't be able to create subclass of it which we saw.

15131 -> All right, it gives you an error some examples

15133.7 -> of final clause in string class.

15136.2 -> So system class

15137.9 -> in Java dot Lang dot package is final as well string class

15142.3 -> that we have been using string class

15144.8 -> that's been exposed by or Java itself has

15147.591 -> or Java by itself defines it that class is final as well.

15151.6 -> If you try to extend string class,

15153.6 -> it would show you an error it would give you an error.

15156.4 -> So system is kind of putting a contract

15159.6 -> or Java by itself is putting a contract or is saying

15163.8 -> that cannot extend the string class.

15165.9 -> You cannot extend Its Behavior.

15167.611 -> You can't change anything any of the behavior

15170.142 -> within your string class by yo,

15171.978 -> that's why they have marked it as final if a method

15174.948 -> is declared as final then it cannot be overridden

15177.8 -> in your child class.

15179.3 -> If a Variable is declared as final then you

15182.1 -> cannot change the value of that particular class

15184.85 -> or cannot change the reference of that particular class

15188.027 -> when it comes to objects.

15189.497 -> So we will see

15190.3 -> that later a Constructor cannot be declared as final.

15194.4 -> So that's the rule you cannot declare the constructors final

15198.3 -> and blank final variable should be initialized in Constructor.

15203.3 -> So maybe in this case

15205.2 -> if you wouldn't have any value here,

15207.508 -> you declared this as final if you don't have any value here.

15211.38 -> It has to be assigned an Constructor right now.

15214.4 -> It's giving an error saying

15216.15 -> that it's not initialized if you mark it

15218.839 -> as for it should be gone.

15220.5 -> So it's mandatory

15221.675 -> that if you put instance variable as Final in class,

15225.2 -> it's mandatory that you assign some value in the Constructor.

15228.905 -> If you don't then compiler

15230.309 -> would throw an error so here you can't override it.

15233.44 -> So basically you have a final method void run

15236.125 -> and you have a sub class

15237.652 -> of vehicle and you're trying to override Run method,

15240.899 -> it shows you an error.

15242.3 -> So this is what we saw in case of was Final

15245.1 -> and when we try to override it in car we got an error

15248.4 -> and it's all compiled sign

15250.1 -> if you declare

15251.089 -> any class as final you cannot overwrite that class

15254.55 -> which we saw it gives you a compile-time error.

15257.8 -> So when it declared a vehicle as final and when you try to extend

15262.275 -> when you try to create car class,

15264.432 -> which extends vehicle class it gave you an error

15267.9 -> because vehicle class was fake lettuce final again.

15270.879 -> This is a compile time.

15272.232 -> Now what's Dynamic binding

15273.762 -> which is also known

15274.8 -> as runtime polymorphism is nothing but during runtime it

15278.603 -> decides which instance of which instance

15281.3 -> of a method should be called

15283.213 -> or which method should be called.

15285.4 -> So this is in case of again inheritance

15288.443 -> and when you override the method in your subclass,

15292.3 -> so we saw this earlier again to just to show

15296.279 -> you we had this move method here

15299 -> and in I have this move method and in automobile management,

15304.1 -> we did this thing we have a Mercedes

15307 -> that is assigned

15308.046 -> to vehicle class class reference rather vehicle class reference

15312.1 -> of reference named by vehicle 1 and in the second thing we

15316.386 -> have vehicle itself.

15317.9 -> So first one is pointing to an object of car,

15321.284 -> which is Mercedes

15322.592 -> and the second one is referring to the object of vehicle itself.

15327.3 -> So this is what dynamic polymorphism is all about.

15330.34 -> The first one gives a call to the move method

15333.122 -> in car the second one second one gives a call

15336.104 -> to the move method in vehicle.

15338 -> So yeah, you could see here.

15339.8 -> So move in car class

15341.3 -> and then it calls a moving vehicle class

15344.5 -> and it happens at run time.

15346.171 -> That's why it's runtime polymorphism.

15348.4 -> So abstraction is a mechanism

15350.7 -> of hiding the implementation details from the user

15354.6 -> and only providing the functionality of a user.

15357.6 -> So basically you could have abstraction.

15359.634 -> We're in on the first day.

15360.996 -> We spoke about the shape class and the circle class

15363.8 -> and Wrangle and square and stuff like that.

15366.3 -> Right?

15366.747 -> So basically shape is a class which is abstract class,

15370.5 -> which doesn't know all the functionality up front door.

15373.2 -> It doesn't have all the behavior of front.

15375.809 -> It doesn't know

15376.722 -> what would be the behavior of a circle class

15379.481 -> or it doesn't know.

15380.7 -> What is the behavior of a square class

15383.225 -> when I see Behavior.

15384.611 -> It's nothing but calculation of area calculation

15387.962 -> of area is nothing but it adds Behavior to the class

15391.6 -> and calculation of area

15393.9 -> in your Square class would be different calculation of area

15397.7 -> in your circle class would be different.

15400.137 -> So shape by itself doesn't know

15402.074 -> what the implementation of area method I would say.

15405.2 -> So that is what is attraction.

15407.4 -> There are two ways in which you could provide

15409.6 -> abstraction in Java one is by abstraction class,

15413 -> which is not hundred percent abstract,

15415.4 -> which could have

15416.416 -> like abstract methods like area in this case is about Track

15420.1 -> but there could be some methods

15421.876 -> which is same throughout or common throughout all

15424.7 -> the subclasses of shape say for example printing area.

15428.1 -> You just have to have a print statement

15430.139 -> which is printing area for a particular shape

15432.5 -> from the implementation per se

15434.235 -> it's same throughout all the classes area method

15437 -> would be something that is abstract.

15438.9 -> Whereas display area could be something

15441.268 -> that is not an abstract method.

15443.2 -> So in such cases wherein

15444.882 -> you have blend of abstract as well as non abstract methods,

15448.821 -> that's where you use abstract class.

15451.2 -> So it's not hundred percent abstract.

15453.468 -> Whereas in interface it has to be interface is something

15456.9 -> which says that it has to be a hundred percent abstract.

15460.337 -> So interface is altogether a new construct

15462.866 -> that we have in Java

15464.16 -> when it comes to abstract class abstract is just

15467.2 -> a modified to a class.

15468.696 -> So you write class and you just prepend it by abstract

15472.3 -> which makes that class and abstract class.

15474.8 -> Whereas interface is something that is a new construct

15477.8 -> that we are going to see in the coming.

15479.9 -> Slides upset class

15481.181 -> and Abstract methods so abstract method is

15484.3 -> as I said area would be abstract method

15486.8 -> in this case wherein you don't have a concrete implementation

15490.6 -> of area in your shape class.

15493.3 -> That's the scenario in such cases wherein

15496.1 -> you don't have a complete concrete implementation

15499.188 -> of a particular method you would declare it

15501.949 -> as abstract method and if you have an abstract method,

15505.5 -> if you have at least one abstract method

15508.2 -> in your class,

15509.157 -> you have to declare that class as abstract class

15512.37 -> or else compiler would throw an error.

15514.9 -> So whenever you have a abstract class,

15517.5 -> it means that there is at least one method

15519.709 -> within that particular class which is declared as abstract.

15522.952 -> So when you suppress this abstract class so

15525.3 -> shape for that matter

15526.621 -> when you subclass shape shape has got a area method

15529.699 -> which is abstract.

15530.835 -> Now when you subclass it when you create Circle,

15533.8 -> which is nothing but class Circle

15535.995 -> which extends shape now you are creating surplus of it.

15539.7 -> That case you have to ensure that you implement area.

15543.3 -> If you don't Implement area,

15545.026 -> it is still kept as abstract and you will have

15547.8 -> to make circle class as abstract as well.

15550.5 -> If you don't give the actual implementation.

15552.93 -> So an abstract method is a method that is declared

15555.7 -> without implementation any class

15557.649 -> that contains one or more abstract methods

15560.06 -> must be declared with abstract keyword

15562.266 -> and abstract class is a class

15564 -> that is declared with abstract keyword

15566.3 -> and abstract class may

15567.992 -> or may not have all abstract methods.

15571 -> So as I said,

15571.901 -> it's a mixture of abstract and on abstract methods

15575.3 -> and abstract class is mostly used for inheritance.

15579 -> So let me take the same example of shape and shapes.

15582.923 -> So we Define a shape which would have abstract area.

15586.8 -> This is what I was saying.

15588.05 -> So when you have at least one abstract method the compiler

15591.048 -> will throw an error.

15592.131 -> So in this case it is saying

15593.7 -> that you have abstract method but your class is not abstract.

15597.1 -> So we have to make this one as abstract.

15599.537 -> And as I said abstract class is nothing but a modifier you

15603.1 -> just have a modifier

15604.1 -> that you need to prepare into the class.

15606.2 -> This is abstract method and you say you have a method

15610 -> which is public void.

15611.9 -> It's not returning anything.

15613.3 -> We are just displaying area now rather than defining it here.

15616.8 -> Maybe I will put something like So we have a shift method

15626.7 -> and now I declare Circle method now,

15630.1 -> this circle method is extending shape now.

15633 -> It's throwing an error and it says you have to implement

15636.666 -> the abstract methods shape

15638.4 -> as got abstract method

15639.604 -> if you don't implement it as I mentioned earlier,

15642.445 -> if you don't implement it

15643.823 -> if you choose not to implement the area method then you

15646.806 -> will have to make this abstract.

15648.511 -> If you make this abstract error would go off.

15651.1 -> But in this case

15652.199 -> since we know the concrete implementation of area

15655.5 -> for Circle will have to implement it

15658.011 -> when I say we will have to implement it we say area

15661.481 -> and we override it.

15662.8 -> So for Simplicity reason,

15664.27 -> I'll just put some value here for now

15666.3 -> since we are talking about abstraction.

15668.29 -> I'll just keep it simple.

15669.6 -> So basically what we are trying to do here is we

15672.504 -> have implemented area

15673.8 -> which would be nothing but your Pi R square actually,

15677 -> so here we have a shape class

15678.914 -> and we are overriding the idea method here.

15681.614 -> And this is how you abstract it.

15683.666 -> When you run it,

15684.753 -> so basically you could have something

15687.2 -> like suppose I create a shape utility class.

15690.127 -> So this is pretty much like overriding methods.

15693.3 -> So you could have a shape class shape circle is equal

15697 -> to New Circle and you could call Circle dot area.

15701.5 -> So basically what you would get is nothing but a float value,

15705.6 -> which is your area area

15707.338 -> of let me put it this way area of circle

15710.338 -> when I want to print it.

15712.184 -> What I would do is circle dot display area

15715.7 -> and I print area of circle

15717.4 -> what we have seen here is there was abstract method area

15720.7 -> which was implemented

15721.981 -> in your subclass that Circle and when I give a call to it

15725.4 -> and here you could see

15726.72 -> that again similar to vehicles that we spoke

15729.249 -> about instance of circle is being assigned to shape

15732.19 -> and when you give a call to it you could see that method

15735.203 -> on circle is being called and not on shape

15737.449 -> because shape by itself doesn't have any implementation of area.

15740.9 -> So one thing to note here is when you have Class.

15744.1 -> So here you could see this value being printed operate abstract

15747.7 -> class would have one or more abstract methods for sure.

15750.514 -> And when you subclass it,

15751.985 -> you have to ensure that you give implementation

15754.5 -> of your abstract methods.

15756.1 -> If you choose not to implemented,

15757.864 -> then you will have to make the subclass

15760.1 -> as abstract as well.

15761.46 -> So execution of abstract method.

15763.643 -> This is very much similar to normal exhibition

15766.626 -> that we have.

15767.516 -> So the main method you have instance of mobile class created

15771.6 -> this case then there's a default Constructor

15774.584 -> of mobile class gets created gets executed.

15777.5 -> So pretty much similar to normal execution

15780.194 -> when you create an instance of Nokia,

15782.5 -> which is subclass of mobile.

15784.2 -> As I said the first statement

15785.8 -> that you have the Constructor of subclass is nothing

15788.8 -> but super or it calls the super Constructor.

15791.34 -> So here we can see

15792.4 -> that the default Constructor for super is being called

15795.5 -> when you try to instantiate Nokia

15797.5 -> as we are running run method,

15799.419 -> but in Mobile class run is an abstract method so

15802.615 -> run method from Nokia class gets executed similar to the example

15806.9 -> that we saw so shape area class area method

15810.3 -> on Circle got executed and not on shape.

15812.8 -> What is the encapsulation

15814.313 -> that encap solution is the methodology of binding code

15817.639 -> and data together into a single unit.

15819.9 -> So basically everything it's a encapsulation.

15822.898 -> It's put as one so you could imagine class

15825.6 -> being put as one right classes called this for that matter.

15829.08 -> You see everything been encapsulated as one right

15832.093 -> you group these together

15833.6 -> you group this integer and long

15836.2 -> which is a property of vehicle and it has got some Behavior as

15839.8 -> through this move.

15840.927 -> It's all encapsulated as one

15842.605 -> or it's all put together as one entity

15844.8 -> that is nothing but encapsulation.

15846.619 -> So basically you could imagine a capsule right

15849.1 -> which has got multiple ingredients

15851.26 -> which has multiple made sense or chemical components

15854.6 -> which are put together into one capsule

15856.917 -> and you have you think capsule has one mixing

15859.613 -> but it's basically combination of chemical components

15862.786 -> Within Thing is for encapsulation.

15864.802 -> There is access modifier comes

15866.683 -> into picture you have this access modifiers

15869.345 -> or private and you have public

15871.309 -> you have protected you have default

15873.512 -> this access modifiers restrict

15875.556 -> or it restricts the visibility

15877.6 -> of regular component of a class say method

15880.312 -> or variable or anything.

15881.9 -> So that's encapsulation feature of object-oriented programming.

15885.8 -> You can't see everything.

15887.05 -> It's not that everything is open for everyone.

15889.3 -> So you can have restriction you have

15891.156 -> different levels of restriction

15892.8 -> when it comes to visibility of this components

15895.447 -> that is a part of encapsulation as well.

15897.7 -> So to achieve encapsulation

15899.7 -> in Java declare the variables as private usually

15903.3 -> the best practices not to expose everything

15906.53 -> because once you expose something as public or once you

15910.9 -> expose it for the application to access you have to ensure

15914.305 -> that you maintain it right because anyone can access it.

15917.65 -> So your class is becoming much more fragile

15920.173 -> a I won't talk about this topics right now

15922.716 -> because fragile D is something that is related to code quality

15926.5 -> or coupling we say

15928 -> so I don't want to touch on that.

15929.6 -> But basically the best practice

15931.762 -> is to have less visibility restrict visibility

15934.9 -> or different visibility as much as possible.

15937.7 -> Try to make it as much less as possible make it private.

15941 -> Basically if you could make all

15942.669 -> the variables as private it would be good thing.

15945.2 -> So basically all non private

15947.2 -> or public variables are liability for application.

15950.352 -> So it increases the maintenance of the application

15953.429 -> and it's easy to break that way

15955.425 -> if you make some changes to a class it becomes

15958.397 -> very difficult the future to maintain it.

15961.064 -> So usually the general practice is to keep the methods variables

15965.265 -> as private not methods variables as private and we have Getters

15969.554 -> and Setters method

15970.8 -> which exposes which are public methods or mutator methods

15974.735 -> which would expose

15976 -> this variable to the outside world through public.

15978.9 -> So usually we don't have Setter methods.

15981.352 -> We restrict Setter methods again.

15983.364 -> Usually you have a private

15985 -> since variable and you have a getter method

15987.1 -> which is a public method

15988.5 -> which is nothing but Returns the value

15990.249 -> of the instance variable to the outside world.

15992.5 -> So data hiding the user will have no idea

15994.715 -> about the inner implementation of the class.

15996.929 -> What are the advantages of data hiding user

15999.426 -> need not know the core implementation of the class.

16002.4 -> It increases flexibility.

16004.058 -> We can make variables and methods read only

16006.8 -> and right only as per the requirement.

16009.1 -> So imagine if you didn't have all this access modifiers,

16012.5 -> there's only one that is public which is exposed to everyone

16015.97 -> so it would create a Havoc.

16017.6 -> So this is basically based on your requirements.

16020.2 -> You could have different patterns

16021.8 -> of this access modifiers used within the application.

16024.6 -> It makes testing easy.

16026.227 -> So basically Hotpoint is reuse ability easy to reuse

16030.01 -> and easy to change with the new requirement.

16033.143 -> So with reusability,

16034.6 -> even the maintainability

16036.066 -> of the particular application is improved

16038.502 -> when you have this encapsulation and easy to reuse in the sense

16042.619 -> if imagine The way around

16044.2 -> where in you have only private methods

16046.7 -> so a class could access only the instance variables

16050.158 -> within a class nothing from outside world.

16052.927 -> It cannot be accessed from outside as well.

16055.7 -> Imagine such a scenario right in that case.

16058.4 -> You would have a lot of code redundancy right everywhere.

16061.235 -> You would write the same code.

16063 -> It might be the same thing.

16064.588 -> We have already implemented in some other class,

16067.174 -> but you will have to re-implement it

16069.1 -> since it's not accessible outside the class.

16071.7 -> So that's how encapsulation increases the reusability of who

16076.8 -> and it makes testing easier.

16078.6 -> Of course.

16079.238 -> So here you could see that employ one.

16081.6 -> So this is the encapsulation mutator method that

16084.371 -> I was talking about.

16085.589 -> So basically you have employee one

16087.559 -> which has got string name,

16089.179 -> which is private you could see here.

16091.287 -> It's defined as private when I say private this name property

16094.9 -> would be used only within this class.

16096.9 -> If you try to access it

16098.177 -> from outside class you would get an error

16100.6 -> but there might be scenarios in which you want to Says this name

16104.567 -> from outside class you want to understand what

16107.4 -> its value is in that case.

16109.3 -> You would have something like this right?

16111.689 -> You would have getter method get name,

16113.912 -> which is nothing but it's written type is string

16116.677 -> which is the data type for name

16118.525 -> and it's returning the name.

16120.233 -> Now one thing to observe here is this is public.

16123.1 -> This one was Private name was private but get name is public

16126.8 -> which means it could be accessed from outside as well.

16129.5 -> Similarly.

16130 -> You could have Setters which is not a good practice.

16132.5 -> By the way, you shouldn't have Setter methods.

16134.983 -> So again Setter is something like you pass the value

16137.983 -> that you want to set this particular name variable.

16140.7 -> So basically you are saying that whatever you send

16143.3 -> through this method is going to set to the name variable.

16146.1 -> So we are referred

16147.4 -> to this particular example in Maine.

16149.447 -> So you create an instance of employee one

16151.8 -> who have edad set name you're sitting at well X

16154.968 -> and when you access it you do e dot get name.

16158 -> So basically what we are trying to say here is

16160.8 -> a demo end caps is a Glass

16164 -> it's not the same class.

16165.6 -> So you have employee one and you

16167.483 -> have demo end caps as a different class though.

16170.2 -> It's a different class

16171.3 -> till you are able to access your name employee name

16175.3 -> from this class.

16176.4 -> This is again,

16177.164 -> a private instance variable you are able to do this just

16180.486 -> because you have this Getters and Setters,

16183.055 -> let understand interfaces interfaces are nothing

16186.2 -> but could imagine interface as a blueprint

16189.5 -> or it is something that it's a specification rather,

16192.6 -> right and interface could be thought of as a specification.

16195.8 -> This is how it should be.

16197.4 -> So basically it could be a company manufacturing bottles

16201 -> or remote rate.

16202 -> It would say that this is

16203.5 -> how it should be basically there should be so-and-so buttons.

16206.5 -> There should be this button should be here.

16208.6 -> This button should be there and something of that sort.

16211.458 -> So basically through interphase

16213.1 -> what we do is we specify the contract we say

16216.155 -> that this is how it should be now.

16218.5 -> For example,

16219.4 -> you could have specification mentioned in a piece of paper.

16222.9 -> This is how Remote should be

16224.6 -> and there could be different vendors for this remote

16227.6 -> who would be actual manufacturing remote

16229.9 -> and which would be aligned

16231.2 -> to this particular remote specifications.

16233.5 -> Then you could check that.

16234.9 -> Okay, so and so specifications are met which means

16237.677 -> that this this particular thing could be used as a remote.

16240.741 -> So basically these are nothing but the specifications

16243.8 -> for the system so through interphase you say

16246.171 -> that this is

16246.839 -> how it should be and you would have different vendors

16249.898 -> or you would have different implementations

16252.3 -> that align to the specifications

16254.316 -> and if they match up to the specification,

16256.9 -> it means that it's a correct one.

16258.5 -> So hence an interface contains all the specifications

16261.966 -> and can be used for creating a new remote.

16264.802 -> So all you see here,

16266.119 -> there's a joystick this AC remote

16268.2 -> this TV remote and everything.

16270 -> It has got different things

16271.51 -> but there's something in common and that's

16273.73 -> what you specify

16274.638 -> through interface and interface contains variables and methods

16278.1 -> but the methods declared

16279.8 -> inside interface or by default abstract methods.

16283.2 -> As we saw in the earlier slide interface is

16285.958 -> hundred percent abstract.

16287.6 -> So all the methods that you have within interface is abstract

16290.6 -> and interface is used to achieve abstraction.

16293.188 -> It is used to achieve

16294.461 -> loose coupling when I say loose coupling.

16296.886 -> It's like you are not binding everything into a class.

16300.1 -> Basically you say that fits a remote.

16302.6 -> It has to have this features, right?

16304.9 -> So basically your kind of decoupling it or you can see

16308.498 -> that all the implementations

16310.4 -> of remote will have so-and-so specifications,

16313.489 -> which is been introduced by interface also in Java,

16317 -> you cannot have multiple inheritance.

16319.135 -> You cannot have a class

16320.5 -> which extends multiple classes cannot have car

16323.787 -> which extends vehicle and which extends the for example

16327.7 -> locomotive locomotive is one of the classes

16330.6 -> if for example,

16331.642 -> so, you cannot have a class

16333.45 -> which extends to classes that is multiple inheritance.

16337.3 -> Do you could have levels

16338.71 -> and you could have hierarchical inheritance,

16341.047 -> but you cannot have multiple inheritance.

16343.4 -> But through interfaces you can have multiple inheritance

16346.8 -> you could parlament multiple interfaces,

16349.3 -> but not multiple classes again,

16351.413 -> since this is

16352.3 -> inheritance interface is hundred percent abstract class.

16355.993 -> And basically you create sub classes

16358.38 -> from or you implement an interface is nothing

16361.268 -> but it follows he's a relationship.

16363.5 -> So what's the difference between interface and a class

16366 -> and interface can never be instantiated

16368.052 -> just to give you an example,

16369.7 -> I'll show you what interface is.

16371.604 -> So instead of this class.

16373.141 -> I will make this interface.

16374.8 -> So this is how we Define an interface we Define interface,

16378.734 -> but as I said,

16379.7 -> the interface is hundred percent abstract.

16382.111 -> Everything has to be attract.

16383.7 -> You cannot have methods something of this sort.

16386.9 -> You cannot have a concrete implementation of method though.

16389.8 -> You could have a default method which we would be looking

16393.1 -> at in the in the slides to come but at this point,

16396.289 -> let's imagine that you have a ship class and

16399 -> whatever methods you have you declared

16401.4 -> within your ship class has to be Track a by default.

16404.5 -> It is abstract.

16405.464 -> You did not even mention it

16407.134 -> by default jvm puts it has abstract.

16409.3 -> Even if you mention it abstract, it's not a problem.

16412.1 -> It is abstract.

16413.2 -> So now when I unlike extends

16415.6 -> that we do on glass or for the face you implement it

16421 -> so you implement shape class.

16423.4 -> So you'll have to make it public by default the access modifier

16427.2 -> for a method the face is public.

16429.155 -> So here you can see

16430.352 -> that we have implemented it we could see

16432.756 -> that it has a hundred percent abstract.

16435.1 -> So with this you could see most of this differences

16438.153 -> being listed here and interface should contain abstract methods,

16441.958 -> which we saw class can contain only concrete methods.

16445.1 -> We are talking

16445.873 -> about normal class here not the abstract class.

16448.579 -> The members of the interface are always public

16451.1 -> which we again saw

16452.2 -> when I didn't implement

16453.688 -> this one as public Circle it gave me an error.

16456.563 -> So by default it is public

16458.298 -> the members of the class can be private public

16461.3 -> or protected and interface can I have a Constructor

16464.9 -> since we are not creating instance.

16466.9 -> The first point you can see that interface is

16469.4 -> cannot be instantiated since we cannot instantiate interface.

16473.2 -> There's no need of Constructor a class can have constructed

16476.566 -> to initialize the variables

16478.1 -> which we met yesterday implements keyword is used

16481.3 -> for inheritance and whereas in terms of class,

16484.829 -> we have extends

16486.1 -> which we saw now right for interfaces you we

16489.163 -> changed it to implements rather than exchange

16492.188 -> after extends keyword.

16493.7 -> Any number of interfaces can be given this

16496.169 -> is multiple inheritance that we spoke about

16498.7 -> whereas after extends

16500.5 -> you can have only one and only one class.

16503.097 -> You cannot have multiple classes cannot contain instance Fields.

16507.38 -> The only field

16508.311 -> that can appear in our interface must be declared

16511.423 -> both static and final can contain instance Fields.

16514.676 -> So only the constants would be declared

16517.169 -> when your interfaces whereas with in class.

16519.9 -> You can have all levels of all the instance variables.

16523.4 -> Classes have implementation

16525.2 -> whereas this is between class and abstract class.

16528.4 -> So classes have implementation abstract classes have

16531.628 -> no implementations or they can have implementation as well.

16535.3 -> So it's a mixture

16536.3 -> of abstract methods and non abstract methods

16539.32 -> as we saw.

16540 -> So abstract class is not hundred percent abstract

16542.5 -> right unlike interfaces.

16544.034 -> You could have concrete implementation

16546.4 -> as well concrete classes are instantiated to create

16549.718 -> object abstract classes

16551.198 -> cannot be instantiated similar to interfaces

16554.15 -> abstract classes cannot be instantiated a concrete class

16557.8 -> can be final and abstract class can never be final

16561.646 -> as it has no defined functions

16564.1 -> for abstract class to be a complete.

16566.531 -> It has to be extended.

16568.1 -> That's what the focus is abstract class

16570.9 -> and interface is an abstract class can be extended

16574.738 -> with class using keyword extends

16577.3 -> and whereas interface

16579.2 -> can be implemented to a class using implements

16582.3 -> which we saw.

16583.2 -> Abstract class can extend only one class at a time

16586.6 -> and interface can extend number of interfaces at a time.

16590.4 -> So yeah, this is one thing we're in your interface can extend

16594.148 -> other interfaces, right

16595.423 -> and you could have multiple interfaces

16597.8 -> extended abstract class can have private default protected

16601.5 -> and public members

16602.7 -> and interface members are default or by default public

16607.3 -> in abstract class keyword abstract is mandatory

16610.723 -> to declare a method as an abstract method

16613.8 -> which we saw okay in interphase.

16616.039 -> It's not mandatory

16617.265 -> because by jvm by default put set abstract classes

16620.6 -> are to achieve zero to hundred percent of abstraction,

16623.453 -> which means that you

16624.535 -> could have some concrete implementation as well.

16627.3 -> Whereas interfaces or hundred percent abstract.

16630 -> You cannot have anything you cannot have any implementation

16633.2 -> within but you could have a default methods abstract class

16637 -> can have abstract

16638.1 -> and on abstract methods again here abstract class

16641.7 -> can have Constructors.

16643.2 -> Interface cannot have Constructors which we

16645.979 -> saw earlier abstract class

16647.694 -> can have abstract and non abstract methods

16650.5 -> since it's not a hundred percent abstract.

16652.8 -> Whereas interface can have only abstract methods by the way

16656.97 -> from java it as I said,

16658.624 -> there's a default method being introduced

16661.3 -> which is nothing but

16662.434 -> you could have a concrete implementation written

16665.1 -> within interface class interface relationship you have class

16669.525 -> which extends other class

16671.42 -> you have class

16672.6 -> which implements interface you have interface

16676 -> which can extend other interface

16678.2 -> if there's an interface already defined and you want to inherit

16681.847 -> some methods or you want to inherit the methods

16684.332 -> that you have within the other interface

16686.6 -> would do it using extends a class extends another class

16690.2 -> while implements an interface

16692 -> and interface extends another interface class

16694.992 -> cannot extend multiple classes,

16697.1 -> but can Implement multiple interfaces.

16700.2 -> So here you could see that this one class.

16703.054 -> Which is extending the class on the top

16705.8 -> and this one at the right side.

16707.878 -> It's time to extend it.

16709.343 -> If you try to extend multiple classes,

16711.7 -> it would give you a compile-time error.

16713.9 -> It won't allow you to inherit from multiple classes.

16717 -> Whereas in this case,

16718.416 -> you could see it's implementing multiple interfaces on the top.

16722.6 -> You could see one interface been implemented by this class

16725.952 -> and there's one more interface to the right

16728.3 -> which is being implemented by this class class

16730.9 -> cannot extend multiple classes,

16732.7 -> but it could Implement multiple interfaces

16735.451 -> which gives an opening for multiple inheritance

16738.624 -> when any interface gets compiled compiler automatically adds

16742.875 -> access modifiers to the members.

16745.072 -> So this is done by default its internal Edition.

16748.44 -> So here you could see interface demo

16750.834 -> which has got one variable

16752.7 -> that is int count is equal to 10

16755 -> and it has got a method which is output now

16758 -> when this demo dot Java,

16759.773 -> which is an interface,

16761.4 -> which gets compiled you See that by default.

16764.676 -> It has put it as public static final so count 10 would be given

16769.4 -> access modifier public static final so four variables jvm by

16773.595 -> itself puts public static final

16775.8 -> and four methods it would put it as public abstract.

16779.5 -> So that is the reason when we had the area method

16782.3 -> when we try to override it it gave an error saying

16785.182 -> that it has to be public.

16786.8 -> So John went to a bank he wants to credit some money

16790.7 -> to his account.

16792 -> So let's see this one.

16794.1 -> So basically here you could see to implementation of it you have

16797.9 -> money interface and you have operation as its method.

16801.7 -> So now you could see two implementations of it

16804.506 -> one is debit and the other one is credited with in debit.

16808 -> We are just saying

16808.9 -> that we are writing a dummy statement.

16810.7 -> They're saying that we are debating money from this account

16813.6 -> whereas credit is nothing.

16814.99 -> But again, we are printing saying

16816.743 -> that we are crediting money to this account.

16819.1 -> So now when you create instance of money

16821.8 -> or you create in It's off credit

16823.913 -> and assign it to money and money dot operation.

16826.988 -> You would have operation method

16829.01 -> on credit being called in this example.

16831.687 -> We can see that there's a shape interface

16834.4 -> which has abstract area and there's a circle

16837.83 -> which returns this value right and say I declare one more class

16842.8 -> which is square

16844.2 -> which implements shape and its again three main error saying

16847.8 -> that you will have to declare it.

16849.73 -> You will have to implement the method

16851.9 -> so I will read this and say I written some dummy value

16855.7 -> like hundred you have a square and said Circle say circle area.

16861.4 -> We are just hard coding it right now.

16863.517 -> We don't have to implement it.

16865.1 -> So it gives you two hundred.

16867.1 -> It's returning 200 as float.

16868.936 -> And this one is returning hundred.

16871.1 -> So what we can do here is we have this shape utility.

16874.9 -> So here we have this thing called on Circle.

16878.032 -> So I will just print it out here saying

16883.6 -> And now I have one more say for example,

16886.493 -> I create one more shape

16888.2 -> which is square nothing but Nu Square now

16891.4 -> what we are doing is we are going to print out

16894.861 -> where dot area so instead of assigning to a variable

16898.8 -> you could do it this way as well area of a square.

16902.7 -> What we did is we have interface shape

16904.612 -> and we have a area method which is abstract.

16906.941 -> We have two concrete implementations of

16909 -> it Circle and square

16910.4 -> and we are instantiated circle

16912.5 -> and square here and we are calling area method on it.

16916.281 -> By the way,

16917.049 -> you could see here that this is dynamic polymorphism Circle

16921.1 -> and square is been assigned to the shape reference.

16924.3 -> It's not directly to the circle.

16925.9 -> You would see hundred and two hundred mean printer know

16928.6 -> so Circle was 200 and square was hundred

16931.179 -> and you could see two hundred

16933.1 -> and hundred so it's basically Dynamic polymorphisms followed

16937.008 -> in interface as well.

16938.4 -> You could extend an interface with another interface.

16941.7 -> So suppose you have one more Switch is

16944.5 -> for now just too.

16948.7 -> So I create an interface test interface

16951.3 -> which has like test method.

16953.1 -> So you have a test interface which has void test

16956 -> and you could have shape which is extending test interface.

16960 -> Now your circle and your Square would give an error

16963 -> because there is one more method that you need to implement.

16965.95 -> If you don't implement it you will have

16967.85 -> to either make this abstract.

16969.331 -> If you make it abstract,

16970.535 -> it should go off but in this case suppose

16972.829 -> we want to implement it then you will have to ensure

16975.5 -> that you implement test method as well once implemented

16979.1 -> the error should be gone similarly in square.

16981.888 -> You will have to find it.

16983.358 -> So that's what is extending one interface with another right?

16986.7 -> So basically here you could see there's walkable.

16989.2 -> There's a runnable and when you do it

16991.313 -> when you implement runnable,

16992.923 -> you will have to ensure that you implement Walk and Run

16996.1 -> both the methods.

16997.423 -> It's a class extending one class

17000 -> and implementing more than one interface.

17002.702 -> There's two interfaces Walk and Run

17005 -> so you could see animal

17006.675 -> which implements walk and So then it will have to implement

17010.958 -> both the methods Walk and Run

17013.1 -> whereas there's a human glass which extends animal.

17017.5 -> So this is basically there's a class

17019.459 -> which is implementing multiple interfaces

17021.812 -> and which has to ensure

17023.1 -> that it implements both the methods.

17025.448 -> So in this case walk and run it has to ensure

17028.4 -> that it implements Walk and Run and this one class

17031.971 -> which is extending from this particular class

17035.1 -> and you could see here

17036.807 -> that you could assign human which is extending

17040.269 -> which is a subclass of animal

17042.5 -> we could see

17043.1 -> that human could be assigned to walk and run as well since it

17047.216 -> is implemented from there.

17049 -> So you could have H 1 dot walk

17051.2 -> and H 2 dot run sort of you have given a call

17054.32 -> to this methods.

17055.46 -> So basically this is again

17057.241 -> if you understand the idea of runtime polymorphism

17060.6 -> or dynamic polymorphism,

17062.127 -> which is nothing but assigning the instance

17064.8 -> of subclass to superclass you should get idea of me.

17068.6 -> All this thing we are pretty much talking the same thing

17071.9 -> all this is talking about Dynamic polymorphism.

17074.9 -> If you get that thing, right you have good enough.

17077.8 -> So we are talking about default method right

17080.7 -> since Java it you could have default implementation

17084.236 -> within your interface.

17085.732 -> You could say that you cannot have a concrete method

17089.2 -> but you could have

17090.258 -> if you put a concrete methods something like this,

17092.749 -> it would give you an error.

17094.2 -> Okay, it gives you an error saying

17096 -> that it's not allowed but you could have it as default.

17099.196 -> Once you define is default.

17100.794 -> It's good enough.

17101.8 -> So all this methods are all these classes circle square

17106.3 -> and all these classes would get would inherit

17109.05 -> this they can't override it.

17110.8 -> They can't do anything with it,

17112.497 -> but they would inherit this we can give a call though,

17115.4 -> but he can't override it.

17116.926 -> So basically I'll just show it here.

17119.163 -> So basically you have default method

17121.4 -> which is say say and which is printing out.

17124.2 -> Hello.

17124.602 -> Welcome to edu Rekha, right

17126.6 -> and you can see here.

17128.5 -> Flash interface demo,

17129.735 -> which is implementing welcome and you could see here.

17132.602 -> Hello bean concrete implementation of L,

17134.897 -> which is nothing but it's printing out the message

17137.665 -> that is passed to the hello method so

17139.7 -> though default class interface demo doesn't declare

17143.1 -> say method it inherits from welcome.

17145.779 -> When you do out dot say you could see the default method

17150 -> being invoked here.

17151.2 -> We could see that you know,

17152.605 -> hello welcome to edu Drake has been printed out

17155 -> which is nothing but the output of default method so

17157.77 -> basically default methods are not but method

17160.406 -> which cannot be overridden

17162 -> but is available for all the classes

17164.799 -> that implements a particular interface

17167.6 -> or implements that interface

17169.616 -> so rules for using private methods in interfaces

17173.021 -> following all the rules for using private methods

17176.5 -> in interfaces private interface method cannot be abstract

17180.809 -> private method can be used

17182.809 -> only inside interface private static method

17186.152 -> can be called from other static.

17188.614 -> Non-static interface methods private non static methods

17193.115 -> cannot be called from private static methods.

17196.5 -> This might look confusing at this point,

17198.701 -> but you could think that first of all private interface method

17202.289 -> cannot be abstract

17203.194 -> because we want it

17204.134 -> to be implemented in some other implementation, right?

17206.9 -> We cannot keep it private since interface

17209.3 -> by itself doesn't have the implementation of it.

17211.743 -> You want to implement that method in some other class.

17214.5 -> So it cannot be private private method can be used

17217.5 -> only inside interface.

17219 -> So if we Define a private method within an interface,

17222.119 -> it can be used only within the interface.

17224.519 -> So basically you could have a default method

17227.049 -> which is private, right?

17228.569 -> So basically default method itself cannot be private

17231.8 -> but within default method,

17233.673 -> so what I am trying to say is so here

17236.268 -> you could have private void which is doing nothing

17239.8 -> but here your default method would call this private method.

17244.1 -> So private method can only be used within the interface

17247.5 -> and it's usually used 24 get private static method

17250.8 -> can be called from other static.

17252.755 -> This is pretty much similar to other classes normal classes

17256.3 -> private non static methods cannot be called

17259.4 -> from private static methods.

17261.3 -> This is a common rule

17262.6 -> that we have private non static methods cannot be called

17265.611 -> from private static method.

17267.2 -> So if you have a static method within the static method,

17270.3 -> you cannot call a non static method.

17272.381 -> Remember we mentioned it earlier

17274.139 -> unless we create the instance of it.

17276.246 -> We can't call it.

17277.299 -> But in this case you cannot call it at all.

17280 -> So it's not on a class you're invoking it basically

17283.286 -> within an interface.

17284.6 -> So private methods is specifically you could call

17287.6 -> Private methods from within your default method in interface

17291.262 -> and since private methods are not accessible from outside.

17294.8 -> That's the only reason you could have private method

17297.3 -> near interface static methods in an interface.

17301.1 -> So you could have something like this

17303.651 -> where in you have interface one and you

17306.287 -> have a static method display?

17308.3 -> You remember static methods are more

17310.52 -> of a class level method, right?

17312.593 -> You need not have to create

17314.4 -> instance of a class to invoke a static method

17317.4 -> if an interface has a static method you could call

17320.4 -> it directly by interface dot the name of the interface

17323.517 -> does the name of the method

17325.3 -> so we can have a static method like static.

17328.5 -> So this method could be called

17330.6 -> so you could have something like this method

17333.013 -> and you could call it directly using the interface name.

17336.1 -> So we have this so now

17338.2 -> within shape utility you could wreck akahl,

17341.5 -> like as you could see here,

17343 -> you could call the static method

17344.6 -> directly by the name of the interface.

17346.9 -> You cannot have normal methods within it

17350 -> unless it's a default one interface features

17352.311 -> four different jdk version.

17353.9 -> So interface has evolved throughout the versions

17356.9 -> of JD case.

17357.7 -> So just to brief on that.

17359.4 -> We have jdk 121 .7

17362 -> having normal interfaces with constant static variables

17366.1 -> as we said the variables

17367.511 -> that you would have in a The freezer typically constants

17370.5 -> which is public static final and with abstract methods,

17374 -> of course in Java 8 it evolved and we have a default method

17378.8 -> as I said,

17379.6 -> there would be one default method

17381.482 -> which would be inherited by all the interfaces extending

17384.6 -> that interface and you have static methods as well,

17387.807 -> which was not there earlier in Java 9 and later versions.

17391.7 -> So in Industry right now,

17393.746 -> it's mostly Java 8 that's been used across

17396.844 -> very few have gone to Java 9 all the big data Frameworks

17401 -> and everything we have is supporting Java it

17403.9 -> at this point.

17404.878 -> So with the latest version

17406.761 -> that's Java 9 and above we have static constant static

17410.6 -> variables abstract methods default method static methods

17415.1 -> and they have come up with this two methods

17417.253 -> which are nothing but private methods

17419.1 -> and private static method,

17420.484 -> which was not there earlier.

17422.018 -> Now you could have this things as well.

17424.1 -> It makes very little sense to have all this scope variables,

17427.57 -> but maybe they might Have

17428.92 -> or something as a part of evolution,

17430.979 -> but at this point,

17432.064 -> I believe since this private methods cannot be called

17435.195 -> from outside it just

17436.425 -> that you have control over the default method.

17439.186 -> So basically maybe

17440.292 -> if you have a big logic to be written

17442.476 -> within your default method

17444.136 -> just to modularize it just to break it

17446.5 -> into multiple methods not to have one monolith big function

17450.348 -> or big method you could have this private methods.

17453.6 -> That's what I can think.

17455.1 -> What is the package we have been using package since day one.

17458.961 -> So package is nothing but it's a namespace

17461.6 -> it's for avoiding Collision.

17463.9 -> So basically I could write a name class with name shape

17468 -> and maybe someone else

17469.495 -> within my team would write the same thing.

17471.999 -> Right?

17472.36 -> So basically at the end when we archive it together

17475.495 -> like we have a jar file,

17476.991 -> which is Java archive

17478.3 -> when we archive this files together there is going

17480.814 -> to be named Collision, right?

17482.311 -> You wouldn't know which shape class.

17484.179 -> Are you referring to?

17485.3 -> So basically namespace is nothing but it adds.

17488.356 -> Stewart and it avoids Collision classes

17490.936 -> in the same package can access each other's members.

17494.4 -> So basically you can have within a package.

17497.5 -> So we'll talk about the import statements

17499.572 -> that will give you a clearer understanding

17501.814 -> of what we are talking about.

17503.4 -> But basically within a package as you could see here,

17506.4 -> we have not done anything to refer any of these classes.

17509.815 -> So it's within a package we have calmed said Eureka

17513 -> and we have all these classes within this package

17516.1 -> so you could see that employ or maybe manager

17519.3 -> which is a different class in the same package.

17521.814 -> We are accessing it directly.

17523.4 -> We are not doing anything different for it.

17525.5 -> But when you want to access it

17527 -> from a different package you have to do something else

17529.4 -> which is nothing but importing the package

17531.8 -> the normal living convention is usually domain name here.

17535.44 -> You could see we wenshan calm down at Eureka.

17538.411 -> So it's usually something

17540.1 -> of that sort dorji dot example dot hyphenated name.

17543.6 -> It has to be lower case usually written

17545.9 -> in lower case companies use their reversed.

17548.488 -> Net domain name to begin their package names.

17551.2 -> So basically if you have my package or example.com,

17555.15 -> you would have it in reverse order.

17557.4 -> This is typically a one of the best practices of practices

17560.5 -> that's been followed across industry to define

17563 -> the package but it doesn't have any constraints

17565.801 -> from the Java side

17566.835 -> as such you could do anything.

17568.682 -> So for example,

17569.564 -> if I make it uppercase, so basically it's saying

17572.529 -> that it's not showing error because of its in uppercase,

17575.769 -> but basically you don't have a directory starting

17578.576 -> with uppercase Aspire Java or from the Java side.

17581.4 -> You don't have any constraints.

17582.9 -> For example, I could do

17584.2 -> something like So basically it does convert it into lower case,

17589.3 -> even if you give uppercase.

17591 -> I don't know whether this is a feature in IntelliJ IDE,

17594.176 -> or it is of course it has to do something with the ID

17597.319 -> because Heidi is converting it into lower case as

17600.213 -> far as the Java naming convention is concerned.

17602.919 -> This is what we do

17604.048 -> but it doesn't have constraint Java predefined packages.

17607.5 -> So Java itself has many packages.

17610.1 -> So you could imagine the entire language been written

17612.7 -> in Java source code.

17614 -> So basically all this you would find in the source code

17617.333 -> when we refer to the string

17619 -> when we refer to string string is a class

17621.615 -> which resides in Java dot Lang.

17623.642 -> There is Java dot language is nothing but Java dot language.

17627.5 -> So string is something

17629.1 -> that resides in Java dot Lang object is a class

17632.236 -> which is a super class for all the classes.

17635.1 -> So, you know, what super classes are

17637.388 -> after we went through the inheritance thing.

17640.2 -> So you have super class and you have subclasses.

17643.579 -> So the superclass All the classes no matter

17646.6 -> what class you use with in Java.

17648.79 -> All the classes are inherited from a class called object.

17652.6 -> There is a class object

17654.09 -> in Java from which all the classes have inherited

17657.257 -> from our all the class inherit

17658.8 -> from this particular class thread is used

17661 -> for multi-threading.

17662 -> Java dot length of thread

17663.5 -> is used for multi-threading multi-threading is nothing

17666.442 -> but 2 lightweight processes in order to leverage the potential

17669.6 -> of your processors.

17670.782 -> So if you have multi-core,

17672.4 -> then you could have multiple operations happening

17675.035 -> at the same instance of time.

17676.62 -> That's what thread is all

17677.994 -> for you make it faster you have exception class

17680.899 -> you have system class Java dot language system.

17683.8 -> This package is used to achieve the language functionality

17686.65 -> such as conversion

17687.5 -> of data from string

17688.677 -> to fundamental data display the output on the console

17691.9 -> and many more the package is quoted by default.

17694.8 -> So you don't have to specifically explicitly import.

17697.8 -> This particular package is

17699.414 -> by default voted into your application Java dot util.

17702.537 -> This is like utility classes you have Elections

17705.554 -> and stuff like that into your Java dot

17707.8 -> util this package is used for developing quality

17710.765 -> or reliable applications in Java or J2

17713.1 -> ee this package contains various classes and interfaces

17717 -> which improves the performance of j2me application.

17720.294 -> So basically these are utility classes.

17722.8 -> It does something in terms of performance

17725.152 -> or does some conversions or something of that sort.

17728.094 -> Java dot IO is a package which contains something

17730.629 -> like file input stream file output stream

17733 -> and stuff like that,

17734 -> which is basically

17735.142 -> for interacting with your files with your I/O.

17738 -> So basically if you want to load something into your memory,

17740.602 -> if you want to read something from your file

17742.5 -> or write something go file in your local directory,

17745 -> you would use something like Java dot IO package

17748.1 -> if you want to do some kind of socket networking or some kind

17751.965 -> of network programming you would use java.net

17755.099 -> which has something like socket datagrampacket

17758.076 -> datagram socket Etc.

17759.4 -> We have applet tablet is nothing but application

17762.249 -> that gets loaded into your browser.

17764.359 -> It's not you.

17765.133 -> So as of now earlier it is to be used

17767.251 -> but now there are a lot of other technologies

17769.7 -> that have come up but this is something

17771.917 -> like an applet is a Java program

17773.8 -> which runs in the context of w WR world wide web for browser.

17777.9 -> You have Java dot e WT which is like event-driven

17781.285 -> like you could have UI applications.

17783.7 -> If you click on your checkbox

17785.6 -> or button there would be even triggered

17787.8 -> and you would have an event handler handling it

17790.2 -> if you click on a mouse

17791.298 -> or something you would have a even triggered.

17793.4 -> So basically all these classes are grouped into this package,

17796.7 -> which is Java dot AWD

17798.398 -> so you could see the Java dot w dot even

17801.398 -> which has like Mouse listener.

17803.7 -> This is specific to event without this classes.

17807.022 -> It is impossible to handle

17808.9 -> events generated by G UI components.

17811.8 -> So as far as the front end

17814.1 -> is concerned as far as all this a WTF

17816.5 -> that is concerned.

17817.718 -> It's not in use basically.

17819.412 -> Java is much more useful in terms of back and program

17822.8 -> which means you take data and Do something with your data

17826.41 -> and stuff like that,

17827.7 -> but it's not well suited for UI applications

17831.4 -> and it's not used to that extent in Market or industry.

17835.2 -> You have Java dot SQL

17836.813 -> which is nothing but your database related stuff.

17840.5 -> So we want to connect

17841.862 -> to your post gray or if you want to connect to Oracle.

17845.3 -> You have all the stuff written in Java dot SQL.

17848.5 -> So mostly in Java data skill,

17850.175 -> you have interfaces and this interfaces

17852.411 -> as I said,

17853.017 -> it's nothing but specifications

17854.9 -> and this specifications are implemented by database vendors.

17858.75 -> So it's nothing but interface is just

17861.1 -> an abstract method it would have like four five abstract methods

17865 -> within so all this concrete implementation.

17867.753 -> Someone will have two women to use this interfaces

17870.837 -> or someone will have a class

17872.6 -> which will implement this interface has and we

17875.3 -> as developers can use those classes

17877.3 -> to interact with databases.

17879.3 -> So Wenders like Oracle will have its own set of implementation

17884.2 -> to the Patients

17885.4 -> that are mentioned in Java dot SQL

17887.893 -> as I said most of the thing in Java dot SQL or interfaces.

17892.2 -> So about the access modifier.

17894.096 -> We have spoken earlier.

17895.593 -> We have public we have protected private and default modifier

17899.5 -> public is nothing but it could be accessed

17901.6 -> from anywhere within your application.

17903.807 -> So you could have your methods as public you could have

17906.512 -> your class as public

17907.688 -> you could have your instance variables as public

17910.234 -> which means that particular method could be accessed

17913.054 -> from anywhere within your application.

17915.1 -> You could have protected modifier protected modifier is

17918.276 -> nothing but your subclass is can access it

17920.7 -> and your current package whatever the package

17923.488 -> in which a particular method

17925.184 -> or particular class resides in which you have protected method.

17929 -> You could access it from that class

17931.2 -> or any class from that particular package access

17934.191 -> the protected methods defined within a class that package

17937.7 -> so I will give you an example

17939.534 -> since we have spoken about inheritance now,

17942.238 -> so I will give you a demo on protected private.

17945.2 -> Modifier is basically it's private.

17947.5 -> It's within a class.

17948.7 -> You cannot access it from outside.

17950.368 -> If you try to access it,

17951.499 -> you would get a compile time error saying

17953.5 -> that it's not visible default modifier is package is public

17957.8 -> within package So within package any class can access it.

17961.712 -> So basically it's

17962.9 -> like protected right protected can be accessed

17966.025 -> within the package plus it has like

17968.219 -> if a sub classes are outside the package,

17970.9 -> even though subclasses can access it

17972.859 -> whereas in default.

17974.062 -> It's just within the package.

17975.9 -> So protected has wider scope then default modifier.

17979.574 -> This is kind of public so public has almost like everything so

17983.953 -> why didn't scope then comes protected then comes default

17987.9 -> and then comes private so access modifiers public word Republic.

17991.855 -> So when you have

17992.811 -> Public Access modifier within a class in this case,

17995.8 -> you have two packages.

17996.962 -> Are you Ricardo back one

17998.23 -> and a new record out back to and you have some public members

18001.6 -> within your class one,

18002.7 -> which we can see here that all this public.

18005.19 -> Members could be accessed by Class 2 class 3,

18007.807 -> which is there in the same package as class 1 that is

18010.866 -> at Eureka dot Pack 1.

18012.174 -> So now there are two classes in a do record back

18014.938 -> to one is a class

18015.922 -> which doesn't have any relationship with glass

18018.569 -> one but still it can access it though.

18020.597 -> It's there in a different package.

18022.5 -> But still it can access the public members of class one.

18025.9 -> You can see class for which is a child of last one

18029.9 -> since it extends class one,

18031.7 -> but it's there in a different package

18033.961 -> but still it can access the public members of class 1 so

18037.3 -> protected protected is nothing

18039.1 -> but it could be accessed within the package in which

18042.1 -> the class is defined and it could be accessed by members

18045.614 -> that are outside the package but child of that particular class.

18049.5 -> So in this case we can see

18051.1 -> that there are few protected members in class one

18053.938 -> which could be accessed by Class 2 and class 3

18056.6 -> since they are in the same package as class 1 plus 3

18059.982 -> and class two are defined in Eddie cannot pack 1

18063.1 -> we have class 5 Is not related

18065.7 -> to class 1 which means it's not a subclass

18068.8 -> or it doesn't have

18070.018 -> any relationship with class 1 in that case class

18073.2 -> 5 cannot access any protected members within class 1.

18076.8 -> So here we have class for which extends class 1 which is nothing

18081 -> but plus 4 is a subclass of class 1 which is there

18084.6 -> in a different package at your record back

18087.273 -> to but it can access the protected members

18089.693 -> of class one

18090.4 -> since it is there in a different package

18092.585 -> private member is nothing but it can be accessed just

18095.5 -> within the class in which it is Define.

18097.9 -> So in this case you could see that this is private members.

18101.6 -> So you have class one which has got private members

18104.7 -> and you can see that class to contacts

18106.896 -> is it class three contacts?

18108.5 -> Is it either class 4 or plus 5 no one can access it.

18112.001 -> It's just that class one can access private members.

18115.481 -> So we have seen this in examples

18117.61 -> that we took in session one default package.

18120.4 -> So default package is nothing

18122.2 -> but only within the package in which it is defined.

18125.1 -> It so in this case you have class one

18127.72 -> which has got default members with default scope

18131.047 -> and you can see that class 2 and class 3 can access it

18134.8 -> but not class 4 and Class 5 since they are

18137.533 -> out of this package

18138.8 -> since Class 2 and class 3 are defined in the same package

18141.5 -> as class 1 that is a deal-breaker DOT back one.

18143.875 -> That's the reason you could access from there.

18146.2 -> This is same for attribute or method.

18148.7 -> There's a table here,

18149.949 -> which is summarizing whatever we discussed so far you

18153.007 -> have modified public.

18154.167 -> So yeah, it's within the class.

18155.813 -> Yes.

18156.052 -> It's within the package.

18157.427 -> Yes, if it's within the subclass.

18159.309 -> Yes and within the world days

18161.093 -> so everywhere it could be accessed right?

18163.638 -> That's why you have public protected is within the class.

18167.3 -> Yes, within packages within subclass.

18170.099 -> Yes, but not within world.

18172.06 -> So just within package and subclass,

18174.7 -> but if you have

18175.553 -> different package or if you have different package,

18178.4 -> but it's not a subclass.

18179.6 -> Then you can't access it.

18181 -> No modifier,

18181.7 -> which is a default scope within the classes

18184.3 -> within the Yes,

18185.242 -> but we saw

18185.838 -> that it cannot be accessed within the subclass

18188.623 -> if the subclass is in a different package

18191.1 -> when we save world world is nothing but any package

18194.324 -> and they are not related in this case the previous example

18197.973 -> that we should saw last five is something

18200.622 -> that could be thought of as laws that are unrelated.

18204 -> But reside in a different package private is just

18207.2 -> within the class you can see

18208.9 -> that it's not with package within the package.

18211.3 -> It's not within the subclass.

18212.822 -> It's not within the world.

18214.2 -> So I think we have spoken

18215.7 -> about private public and default scope earlier.

18218.806 -> Let's start off with protected.

18220.9 -> So in the meanwhile when it starts,

18223 -> let's talk about this.

18224.4 -> So here we can see package demo

18226.443 -> which shows public it has got a public method

18229.198 -> that is message.

18230.2 -> There are three ways to access the package from outside.

18233.004 -> So let me talk about how we actually recorded.

18235.318 -> So there are three ways to access the package from outside.

18238.3 -> The package one is with import this case

18241.2 -> like you had a direct a 1 and enter a car to right there.

18245 -> Sample that we saw earlier.

18247 -> I do record Pack 1 and add

18248.544 -> you taken right back to these are the two packages you have

18252 -> if you want to access something you want to access

18255.1 -> class 3 from class 5 you would have to import

18258.9 -> a new record Pac-12 class 3,

18261.5 -> since it is outside the package

18263.691 -> of back one if it's within the package so far

18266.8 -> the examples that we were taking was all

18269.094 -> within the same package,

18270.337 -> so we didn't have to import it now.

18272.1 -> I will just show you an example wherein you would have something

18275.3 -> that is outside the package and I will show you

18278.2 -> how to access it.

18279.236 -> So we have to import it.

18280.7 -> So whenever you have it in different package,

18283 -> then you have to input that particular package

18285.4 -> within one thing is importing the entire package.

18288.496 -> The other one is importing a particular class.

18291.4 -> So in this case you have a package demo,

18293.708 -> and we can see that within package demo.

18296.006 -> There's a pack demo,

18297.186 -> which is nothing but a class defined within it.

18300 -> So, let's see

18301 -> how to access package from another package

18304.1 -> you have a Demo here

18305.9 -> that's a class that is defined within the package demo

18309.017 -> as you could see here.

18310.5 -> There is one method which is MSG and

18313.1 -> which is taking two parameters as input TJ Ryan integer J.

18316.6 -> So what are the ways

18317.76 -> in which you could access this particular class

18320.588 -> that is packed demo from outside the package.

18323.4 -> So the first thing

18324.566 -> that you could do is you could import

18326.908 -> the entire package itself.

18328.6 -> So demo dot star or demo dot asterisk

18331 -> as you could see here,

18332.408 -> which says that all the classes within this particular package

18336.43 -> can be accessed from this particular class.

18339.2 -> So you have a package demo class defined here,

18342.9 -> which says import demo dot star

18345.4 -> and which would input everything all the classes within demo.

18349 -> So in this case back the more you could see

18351.7 -> that pack demo class could be accessed

18354.129 -> from within package demo class

18356.1 -> that's there in different package.

18358.2 -> So basically this package demo class

18360.533 -> that you see here is defined

18362.428 -> in some other package other thing is See

18365.174 -> if you want to import just a class

18367.498 -> and not the entire package.

18369.4 -> You could do that thing as well.

18371 -> So here what we are doing is import demo dot pack demo.

18374.823 -> So we are importing a specific class

18377.3 -> and not the entire package that could be done as well.

18380.5 -> And the third one is instead of importing you

18383.4 -> can do one thing you can have fully qualified path name

18386.714 -> or fully qualified name like demo dot pack demo.

18389.659 -> That's your class name.

18391.062 -> You can access it within your class.

18393.2 -> So basically you would use the fully qualified name

18396 -> who might use it.

18397.3 -> You did not do it,

18398.6 -> but you might use it in case where you're just using it once

18402.277 -> within your class,

18403.4 -> but you would go with this options demo dot pack demo

18407.169 -> or demo dot star in which you class has multiple is referring

18411.539 -> to the class in different package multiple times.

18414.928 -> So in that case,

18416.119 -> you just do it once and could be used

18418.706 -> within your class.

18420 -> You need not do it again and again,

18422.4 -> so I create a new class

18424.169 -> which is Calm down at Eureka new DOT.

18431.6 -> So I created a new package.

18433.6 -> So there is one that is calm down Eddie Rekha,

18436.286 -> and the other one

18437.3 -> that is calm dot ed u de canoe this are

18439.535 -> different packages you have

18441.1 -> if you want to use something within this package

18443.7 -> Comdata Rekha suppose I want to use Vehicles, right?

18447.5 -> So this is what I was talking about.

18449.9 -> When you try to access it.

18451.6 -> You can't do it you can access vehicle from here

18454.4 -> because it's there in a different package.

18456.617 -> Now you are not able to access it

18458.5 -> because you haven't imported it.

18460.7 -> So what I do here is import calm dot Ed u--

18464.4 -> Rica dot vehicle

18466.6 -> once I do this I am able to access it now.

18469.6 -> Now what I was saying is

18471.239 -> if you are accessing multiple classes from multiple classes

18475.206 -> within the package

18476.44 -> like car also you

18477.566 -> are accessing so instead of writing it like this.

18480.871 -> So what you would do is calm

18482.8 -> down at Eureka the car now the compilation error has gone.

18487.5 -> So basically instead of doing this like instead of writing.

18491.54 -> Multiple times the other option

18493.7 -> that we have is like calm down at Eureka dot star.

18499.1 -> So now if I get rid

18500.676 -> of this 2 inputs still it would work.

18503.7 -> I don't need these two inputs

18505.4 -> because we have putted all the classes within the package.

18508.9 -> So it's able to access both the classes vehicles

18512.1 -> and Ed Eureka from calm dotted Eureka.

18514.8 -> The other one was you

18516.4 -> could get rid of this now it's showing up error.

18520 -> What you could do is calm down Eureka dot vehicle.

18524.2 -> You could access it directly with the fully qualified name

18527.7 -> so you can see the error has gone.

18529.4 -> So these are the three ways in which you could access

18531.8 -> different packages

18532.9 -> or access classes from different packages.

18535.4 -> Now, let's understand.

18536.569 -> What is the regular expression

18538.146 -> so regular expression pretty much similar to other languages

18541.314 -> that you have regular expression is nothing but an expression

18544.6 -> through which you could extract some sequence

18547.1 -> of characters from your string

18549.037 -> or you could check

18550.222 -> whether a specific Fake regular expression or

18553.035 -> whether a string is aligned to a particular regular expression.

18557 -> So you could Define a regular expression saying

18559.2 -> that if for example email ID,

18561.113 -> right one of the use cases of regular Expressions could be

18564.774 -> like you have email IDs and you might have seen on websites

18568.5 -> where in you do some kind of registration or something

18571.7 -> and if you don't give a proper syntactic 1 then

18574.6 -> what it would do is it would give you an error

18577.26 -> at the red gmail.com.

18578.553 -> If you don't give

18579.6 -> that it would throw you an error showing

18582.005 -> that it's not proper.

18583.345 -> So it's not checking against the Gmail server to see

18586.6 -> whether your email ID is proper or not.

18589.218 -> So it is just checking syntactically.

18591.708 -> You might have seen it.

18593.264 -> So if you give a wrong syntactic email ID and

18596.366 -> if you go to the next tab,

18598.2 -> if you tap to the next column or to the next space

18601.9 -> what it would show is you haven't entered it correctly.

18605.5 -> So basically what it's doing

18606.9 -> is its checking it against a regular expression.

18609.4 -> It has got a regular expression saying that This is

18611.9 -> how an email ID could be it should end

18614.8 -> with so-and-so characters.

18616.7 -> It should be at the rate.

18618.1 -> It should have at the rate.

18619.549 -> It should have Gmail

18620.725 -> or it should have some characters in between then

18623.4 -> add followed by.com or something of that sort.

18626.248 -> So basically to have

18627.456 -> this syntactic this thing done just to ensure

18630.11 -> that you have given it properly you have a regular expression.

18633.999 -> So yeah, one of the use cases could be to have this pattern

18637.1 -> Checker usually to see

18638.6 -> if you're giving value

18639.7 -> which aligns to what is expected.

18641.798 -> So maybe other thing could be

18643.7 -> if you're typing something or

18645.33 -> if you have been asked to put some amount

18647.683 -> and if you type characters

18649.285 -> there it would give you an error saying

18651.52 -> that it's not allowed those type

18653.4 -> of checks could be done through regular expression or

18656.032 -> if you want some value to start

18657.549 -> with a particular character and end with a particular character.

18660.7 -> You can check it against a regular expression

18663 -> regular expression is a pattern used for searching

18665.5 -> and manipulating strings.

18666.917 -> It could be used for manipulating strings as well.

18669.8 -> So one of the use cases is Ching

18671.823 -> and the other one is for manipulating

18674.1 -> the regular expression either matches the text

18677.334 -> or fields to match.

18678.726 -> So basically it would validate and say

18681.436 -> whether it's a match or it's feeling

18683.9 -> so we call regular expression as Rex which is

18686.1 -> nothing but abbreviation for regular expression.

18689.4 -> So Java supports regular expression,

18691.772 -> and these are the pluses

18693.4 -> that we have with in Java, which is in Java dot util package.

18698 -> So remember we spoke about Java dot util package

18700.8 -> which has got utility classes.

18702.9 -> So these are among them.

18704.935 -> So here you can see a pattern class you

18707.958 -> have mature class

18709.3 -> and you have patterns in tax and tax exception.

18712.6 -> So basically if you have some exception

18715 -> if it's not proper,

18716.171 -> then you would get some exception as well.

18718.7 -> So we would be taking an example clarify what this is all about.

18722.7 -> So here are some matching patterns used

18724.805 -> in regular expression.

18726.1 -> So it just about to read through it.

18729.3 -> So you have like ABC It means it has to exactly

18733.1 -> match ABC if the string

18735 -> that you are matching it against has the content

18738.1 -> ABC it would match

18739.5 -> when you put it into square bracket,

18741.4 -> which is any letter a b or c should match any character.

18746.1 -> And again if there's a negation if within the square bracket,

18749.548 -> if you have this negation Mark,

18751.288 -> which says that any character except these three characters

18754.7 -> should be matched.

18755.9 -> So if you put D it will match the second case

18759.4 -> if you put a or b

18760.723 -> or c it will match and here it would be from D to Z.

18764.8 -> If you put anything it will match not just alphabets.

18768.4 -> It could be anything any character A to Z.

18771.639 -> So when you say A to Z,

18773.4 -> it says that we are giving a sequence of it, right?

18777.06 -> So we are saying from a it's a range basically

18780.6 -> so it understands range as well.

18783 -> So when you say a -

18784.7 -> Z which means that it is from A to Z here we are saying that

18789.238 -> any one letter or digit.

18791.3 -> Ben sequence so basically you could have uppercase

18794.888 -> and lowercase as well.

18796.5 -> Basically it is saying it should be in sequence.

18798.952 -> It should end with basically

18800.709 -> digit at the N dot is some kind of a wild-card character saying

18804.6 -> that any one character

18806.249 -> except line Terminator must be in sequence.

18809.4 -> This one indicates beginning of line.

18812.4 -> So we say that line should begin with so

18814.858 -> and so you could put some character here

18817.274 -> and we can say

18818.11 -> that if a line begins when Sue

18819.805 -> and Sue character sequence or whatever regular expression

18823.3 -> that we have put in then the entire line matches.

18826.6 -> The other one is end of the line with check

18829.4 -> if any character present

18830.8 -> at the end of the line other thing is word boundary.

18833.939 -> We have an example about this

18835.726 -> so which would give you a clear idea about it,

18838.5 -> but it's more about it cannot be part of a word here

18841.93 -> when we put slash B to the front and the end or to the start

18845.9 -> and the end of a particular character sequence,

18848.5 -> which means that it has to be separate word, but it

18851.6 -> I'd be part of some other word /b to verify

18854.884 -> that any character is

18856.464 -> not present at the word boundary /g to check

18859.7 -> that the character is present

18861.646 -> at the end of the previous match metacharacters.

18864.8 -> So we have /t instead of writing 029.

18867.9 -> You could use metacharacters.

18869.7 -> /d to define DJ

18871.5 -> when you want to Define on digit which is

18874.2 -> like you can see here negation of 029 set,

18877.049 -> which is non digit

18878.3 -> which could be like alphabets peace or anything

18880.9 -> which could be grouped as /t / s is a whitespace character

18887.3 -> who space tabs and stuff like that could be enter

18890.7 -> for that matter is whitespace character

18893 -> /s is a non whitespace character

18895.372 -> which means the actual character rather than white space /

18899.6 -> W is a word character and / uppercase

18903.2 -> W is a non word character you have quantifiers,

18906.761 -> which is a quantifier defines how often an element can occur.

18912 -> So star, which means

18914.4 -> that zero or more times plus which means

18917.533 -> that it has to occur one or more times question mark is it

18922 -> could be no or just one time you could mention the number

18925.4 -> of times you want a particular sequence to occur,

18928.2 -> which could be put into your curly braces

18930.8 -> occurs X number of times x

18932.8 -> you could put a range

18934.267 -> within within your curly braces X comma Y which means

18937.9 -> that it should occur somewhere between X and Y.

18941.1 -> So it's a range you have asterisk question mark

18944.7 -> it tries to find the smallest match.

18947.3 -> This makes the regular expression stop

18949.4 -> at the first match.

18950.6 -> So as and when it finds the first match it would stop

18954.015 -> so we will have a quick demo on regular expression.

18957.3 -> So here before we start off we Define a pattern here.

18960.9 -> Basically, then you could see it is basically saying from A to Z

18965.099 -> and followed by character

18966.697 -> one or more character then we have a check here,

18970 -> which is nothing but a string again.

18971.755 -> Which we are going to check first.

18973.405 -> We compile the pattern.

18974.513 -> This is a regular expression pattern

18976.2 -> that you have you're going to check against.

18978.35 -> So the first thing

18979.366 -> that we have to do is we have to compile this pattern to see

18982.7 -> if it's properly done or not.

18984.6 -> So first thing is to compile it against patent and

18987.7 -> if it's correct up to the mark you would get the instance

18991.2 -> if it's wrong then there would be some kind

18993.6 -> of exception thrown then there is a matcher.

18996.1 -> So once you have the pattern you do pattern matcher

18999.381 -> and you provide the string against which you want to check

19003 -> in this case you have

19004.3 -> happy learning welcome to Eddie break is the string

19006.9 -> that spin past and when you do see dot find

19009.506 -> if this is fine,

19010.5 -> it would return the result true

19012.2 -> and if you remember the while construct it would get in only

19015.8 -> if this is true,

19016.987 -> so it's a loop

19018 -> so it would basically I trait through

19020.5 -> and you could see here

19022.014 -> that it's displaying all the characters.

19024.753 -> I'll quickly run this.

19026.5 -> Let's name the class has pattern Checker now,

19029.596 -> I write a main method now if Remember,

19032.4 -> we had a pattern there

19034.3 -> which was like a to z followed by actress.

19037.8 -> Then we have string against which you want to check

19041.646 -> or you could say simple string to check.

19044.876 -> So we just put this one.

19046.9 -> So once you have this string to check now,

19049.4 -> what we want to do is we want to compile this particular pattern.

19054 -> So what we do patten.com pile,

19056.6 -> so one thing to see here is that's the beauty of using

19060.9 -> the IntelliJ or Eclipse.

19063.4 -> So you could see here.

19065.1 -> This package is already been imported when you use it.

19068.548 -> Unless you have multiple classes with name patterns,

19071.976 -> it would ask you to specifically explicitly

19074.732 -> mention which one you opt for.

19076.7 -> But in this case there was just one pattern class.

19079.8 -> So it imported it automatically then we give the pattern here.

19083.9 -> So basically if this pattern is correct,

19086.6 -> if it's rightly formed syntactically you would get

19090.24 -> a pattern here or so.

19091.8 -> Pat and I believe we have a compiled pattern now now

19095.583 -> what we do is we take this compile pattern

19098.513 -> and I think we have matured here.

19100.8 -> We get the matcher.

19102.1 -> No so matcher would check again string.

19105.4 -> So you have a string to check which would give you matcher.

19109.7 -> So here it's asking me

19111.246 -> which mature do I want I'll select this one

19114.4 -> and you see this one getting in put it here.

19117.2 -> So this is what we have done.

19118.65 -> We have compiled the pattern and we have provided the argument

19121.9 -> against which we have to check as a part of nature.

19125.117 -> We get the instance of matcher.

19127.016 -> So everything is in terms of class.

19129.1 -> This is what object oriented programming is all about.

19132.008 -> You have a pattern which is a class.

19134.067 -> You have a method

19135.067 -> within pattern which is compiling your pattern.

19137.652 -> So this is what object oriented programming is all about.

19140.8 -> Everything is realized in terms of classes and objects.

19144.6 -> This is nothing but the object of pattern class company.

19148.4 -> So now what I do is matcher Dot Find

19152.623 -> I just print this one match her dot check.

19156.1 -> So basically what we are trying to do here is once

19159.5 -> the entire string passes

19161 -> through we are trying to get the substring out of it.

19164.1 -> So when we get the substring from matcher,

19166.9 -> you would get the string indexes begin index and you would get

19171.7 -> matched end as well.

19173.225 -> So when we run it, you should get a PP y

19176.2 -> n so the first character would be trimmed off

19179.4 -> so you could see first character being trained of each line.

19183.3 -> So I'm putting regular expression.

19185.551 -> We saw that Java dot util don't reg ex gets imported.

19189.1 -> Then you have patent then you have string to be checked

19192.417 -> against the pattern and the sentence

19194.638 -> which is to be matched are given A 2 Z means any character from A

19198.68 -> to Z and plus means one or more the sentence check is checked

19202.914 -> whether it matches the pattern or not the strings

19205.901 -> from the sentence which match the pattern are printed.

19209.2 -> So basically here we could see

19211.352 -> that Echizen uppercase and we don't have uppercase here.

19215.3 -> So that's the reason I dreamed of the first character.

19218.9 -> So basically if I add H hear you now eh would match as well

19223.221 -> and it won't cream H or it won't remove edge.

19226.5 -> You should be able to see H as well.

19228.6 -> So yeah,

19229.4 -> as you could see here you have H appearing as

19232.7 -> with previous case.

19233.966 -> It was getting primed of so this one is

19236.5 -> for the word boundary.

19237.798 -> As I said, if you want to have something

19240.092 -> like you want to be sure it's a separate word

19242.458 -> and it's not a part

19243.48 -> of any word you could put something like this.

19246 -> So basically what we can do here is

19249.6 -> so we can mention here something like special are we

19253.523 -> and then in so

19254.8 -> what we are trying to do here is you could see here.

19258.5 -> What we are saying is we want to separate word

19261.5 -> as in we don't want it to be a part of any other word.

19265 -> So here in learning do you have iin?

19267.8 -> It didn't pass it because it's word boundary

19270.8 -> whereas Just a separate word here.

19273.2 -> It just passed this one.

19274.9 -> So if and I remove this one you could have seen two ions.

19279.8 -> That's what I mean to say.

19281.366 -> So now what's exception exception handling is nothing

19284.8 -> but typically so here you could see two ions

19288.3 -> when it's / / be it would be just the ones

19291.6 -> that are complete word instead of matching the word boundary.

19295 -> Let's talk about what are exceptions

19297.029 -> and exception is an event

19298.589 -> which occurs during the execution of a program

19301.4 -> that disrupts the normal flow of the program instruction.

19305.166 -> So to give you an example yesterday,

19307.643 -> we spoke about arrays,

19309.2 -> right if array size is 5

19311.6 -> and if you try to access something more than four like

19315.5 -> if array size is 5 which means

19317.7 -> that the index is range from 0 to 4,

19320.7 -> if you try to access something more than four like

19323.5 -> if you try to access Sixth Element within the array

19326.5 -> it would give you an error saying array index out of bounds

19330.328 -> or if a particular Their object is assigned null value.

19333.779 -> And if you're trying to access that method

19336.4 -> within that particular object,

19338.141 -> you would get null pointer exception

19340.2 -> since it's not instantiated as yet

19342.6 -> when you instantiate it that's when the object gets created.

19346.3 -> But if your reference is pointing to null

19348.611 -> and if you're trying to access something within that reference

19352.253 -> or a class you would get null pointer exception

19355 -> similarly you have like / 0 and stuff like that.

19358.357 -> It's basically something that is not expected

19361.5 -> or something that would disrupt the normal flow

19364.7 -> of program execution.

19366.17 -> When an exception occurs the jvm creates an exception object

19370.3 -> to identify the type of the exception

19372.611 -> that has occurred.

19373.8 -> So basically within itself,

19375.675 -> it would create it or the gold would create it

19378.9 -> so I can create my own custom exception tomorrow.

19381.8 -> If I am writing an application usually in applications.

19385.146 -> That's how we do.

19386.2 -> We write our own custom exceptions.

19388.4 -> I can Define my own exception as

19390.685 -> well if My application something is not working

19394.084 -> or something is not running

19396.051 -> as I would expect it to I would throw an exception

19399.517 -> so that within my application it properly logs

19402.8 -> or it properly prints out in my console saying

19405.5 -> that this is the exception

19407.029 -> that's been triggered due to so-and-so condition.

19409.7 -> So an exception is often referred to as runtime error.

19413.12 -> So here we can see divide by zero exception as an example.

19416.8 -> Now there are different types of exceptions first one being

19419.903 -> checked exception the other one being unchecked exception

19422.9 -> and the third one being error.

19424.7 -> So checked exception is something that happens

19427.429 -> in the compile time.

19428.694 -> What happens is when you have a checked exception when you

19432.3 -> are invoking some method,

19433.913 -> which is throwing a checked exception and okay.

19436.774 -> I don't want to get into the catch block

19439.2 -> as yet because we haven't covered it.

19441.4 -> So this is also called as compile-time exception.

19444.4 -> It means if a method is throwing a checked exception then it

19448.141 -> should handle the exception using the try Clash block.

19451.5 -> It should declare the exception using throws keyword.

19454.6 -> Otherwise, the program will give

19456.482 -> a compilation error whenever there's a checked exception

19459.6 -> that's been thrown out thrown out in the sense

19462.2 -> not at the runtime.

19463.387 -> There could be methods which is throwing an exception.

19466.7 -> So whenever there is a checked exception you have to ensure

19470.5 -> when you give a call to that particular method say

19473.526 -> there is a method X

19474.7 -> which is throwing some checked exception

19476.785 -> which is throwing some checked exception from your application.

19480.1 -> You are trying to access this method X

19482.4 -> when you try to access this method X you have to ensure

19486.158 -> that you are taking care of the checked exception

19489.478 -> that is thrown from X.

19491 -> If you don't take care of it,

19492.829 -> it would give you a compilation error

19495.1 -> when I say when you don't take care of it.

19497.7 -> How do you take care of exception?

19499.7 -> That would be the first question

19501.176 -> that would have come to your mind.

19502.7 -> So when I say you have to take care is nothing

19505.539 -> but you have to catch it.

19507.129 -> You have to handle that exception.

19509.223 -> So try and catch is a mechanism

19511.184 -> through Which you handle the exception.

19513.679 -> So what you would do is Method call or the call

19516.8 -> to X you would put it into a try block

19519.7 -> and the catch block.

19521.2 -> You would say that

19522.498 -> if this particular exception occurs execute

19525.524 -> this block of code,

19526.888 -> that is a Handler for exception X

19529.144 -> or checked exception that is thrown from method X.

19532.6 -> So basically you write a Handler for in the catch block saying

19536.6 -> that this is what I want to do when this exception occurs.

19539.8 -> Once you have that when your program runs even

19542.734 -> if the exception occurs,

19544.23 -> it won't stop at that point it would go

19546.6 -> and check whatever is written and whatever piece of code

19549.935 -> that you have written and it can continue from there

19552.893 -> on it's basically a decision made by the developer

19555.776 -> whether to carry from their own

19557.396 -> or whether you want to break it there whenever there's

19560.284 -> a checked exception you have to ensure

19562.4 -> that you handle it

19563.471 -> either handle it or you say

19565.022 -> that I'm not going to handle this.

19567.019 -> I am just going to throw this off from my method

19569.963 -> or throw this off from the Well,

19571.924 -> I'm executing this method X method X which we spoke

19574.988 -> about which is throwing checked exception.

19577.5 -> I can choose not to handle it and just to throw it off

19580.827 -> to the calling program wherever the execution initiated from.

19584.45 -> So if you don't do that,

19585.9 -> you would get a compilation error unchecked exception

19588.958 -> unlike checked exception.

19590.429 -> It's not mandatory

19591.489 -> that you catch it's not mandatory

19593.43 -> that you handle it.

19594.548 -> So runtime exception basically it could occur any time

19597.694 -> and it's not mandatory

19599 -> that you go and actually handle it.

19601.029 -> So even if you don't handle it jvm would be okay with it

19604.1 -> and it won't give you compile time error.

19606.452 -> So basically these are nothing

19608.1 -> but runtime exception so divide by 0

19611 -> that we spoke about his nothing

19612.788 -> but a runtime exception it's not mandatory

19615.474 -> that you go and actually,

19616.976 -> you know handle it during the compile time.

19619.5 -> You can either handle it or you can leave it

19621.825 -> as is and during the runtime you would get an exception.

19624.8 -> So compiler doesn't check for the unchecked exception.

19628 -> It's done at the runtime now error.

19630.379 -> These are Conditions that are external to the application

19634.462 -> and that application usually cannot anticipate

19637.563 -> or recover from it.

19638.995 -> For example,

19639.9 -> if stack Overflow occurs and error will arise

19643.5 -> they are also ignored during the time of compilation.

19647.2 -> So even the error condition cannot be anticipated

19650.2 -> during the compilation time.

19652.048 -> It's done during runtime.

19653.649 -> Right?

19654.019 -> So one of the classic example is the stack Overflow,

19657.241 -> we're in see for example,

19658.812 -> you call the same methods

19660.381 -> like thousand times not thousand time is too less

19663.279 -> for the stack to get overflowed.

19665.327 -> But suppose you call it

19666.8 -> like million times you call same method right in that case.

19670.9 -> Remember when I said

19671.9 -> when you give a call to the method it goes

19674.229 -> to the call stack, right?

19675.789 -> We have a call stack.

19677.1 -> So it would push something it would push state of class

19681.7 -> or it would push the properties

19683.806 -> that's been passed as

19685.175 -> an argument the class or to the method to the stack.

19688.5 -> I treatable if you call it like million times,

19691 -> what would - you would get stack Overflow

19693.4 -> because basically everything would get into the stack and it

19697.1 -> would basically, you know,

19698.7 -> give you a memory or float or even memory

19701.2 -> for the Heap memory for that matter

19703.2 -> if you create lot of classes

19704.727 -> if you create a lot of instances of classes,

19707 -> you are Heap memory would get overflowed

19709.309 -> and you would get out of memory error.

19711.6 -> Those are classic examples of error.

19714.2 -> So what the hierarchy of exception in Java

19717.3 -> when it comes to classes you have a stable interface

19720.922 -> and then you have error

19722.511 -> and you have exception.

19724.1 -> So exception is further.

19726.1 -> It has got runtime exception.

19728 -> The other ones are the checked exceptions.

19730.5 -> So ioexception SQL exception.

19732.8 -> These are the checked exception.

19734.746 -> This has to be handled

19736.041 -> if there's a method which is throwing one

19738.394 -> of these checked exceptions.

19739.9 -> You have to ensure

19741.2 -> that when you give a call to such methods you handle it

19744.569 -> or you throw it from your method

19746.611 -> to the right side its runtime exception,

19749.095 -> so it need not be handled as I said.

19751.354 -> Divide by zero and stuff like that would be

19754.16 -> runtime exception even array index out of bounds

19757.3 -> and Class cast exception arithmetic exception.

19760.5 -> Then you have null pointer exception

19762.687 -> that we spoke

19763.5 -> about all these exceptions are unchecked exception

19766.9 -> and you need not actually handle it during compilation time.

19771.165 -> So why to use exceptions

19772.9 -> when we execute a given program will get an exception exception

19776.789 -> handling is performed in order to get the output.

19779.8 -> So basically,

19780.7 -> why do we handle exception is nothing

19782.9 -> but to get the program going rather than breaking it

19785.9 -> at that point use

19787.083 -> of exception handling process exceptions

19790.1 -> from program components handle exceptions in a uniform manner

19795.4 -> in large projects.

19797.1 -> So basically, why do we do it?

19799.176 -> So it's done basically

19800.7 -> to get the process going rather than stopping it at that point

19804.47 -> and you could handle it the way you want

19806.927 -> to that 's the reason you have this exception

19809.761 -> handlers give you a simple.

19811.5 -> Example suppose 29 by zero

19815.4 -> what I am trying to print here result

19817.7 -> after dividing 29 by zero.

19819.6 -> So basically when you run this,

19821.298 -> it's not showing up any compile time error.

19823.6 -> It's compiling fine.

19824.9 -> Now when I run it

19826 -> since it's a runtime exception it's compiling fine.

19828.6 -> But when I run it,

19829.72 -> let's see if it throws an exception.

19831.875 -> So as you could see here it throws arithmetic exception

19835.264 -> which is divided by 0 and this is happening

19837.795 -> at the runtime.

19838.7 -> That's why it's a runtime exception

19840.7 -> or unchecked exception

19842.166 -> when a runtime exception occurs program gets crashed

19845.566 -> and control comes out of the program

19847.9 -> as we saw here when we ran it.

19849.9 -> It didn't run this part of it.

19851.853 -> You could see

19852.7 -> that it broke out just right from here.

19855.2 -> So whenever there is an exception

19857.3 -> if you haven't handled it program control would come out

19860.261 -> from there exception handling is done to execute the program

19863.478 -> without getting an exception.

19865.184 -> So handling is done basically to handle the exception

19868.2 -> whenever the exception occurs do some action it.

19871.4 -> It's flexibility to the developer to handle

19874.571 -> it the way they want to and get it going mainly try catch

19878.8 -> and finally our keywords for exception handling.

19882.6 -> So we have a trike at as I said,

19884.753 -> there's a try block

19885.981 -> where in all the suspicious one or wherever the exception

19889.6 -> you think that there could be exception occurring

19892.423 -> could put it into a trike block and in the catch block,

19895.5 -> you would say that if a particular exception occurs,

19898.1 -> this is what I want to do.

19899.5 -> All right, that's the catch block.

19901.259 -> The finally block is nothing

19902.83 -> but no matter the exception is thrown or not.

19905.211 -> A finally block is going to execute at the end.

19907.7 -> So basically finally block is usually used

19910.375 -> to release resources,

19911.719 -> right when you deal with databases

19913.789 -> and stuff you create connections against database

19916.8 -> or you create some socket connections and stuff like that.

19919.7 -> When you do some socket programming finally

19922.1 -> would be a place

19923.041 -> where in once the execution of the method is done

19925.864 -> or execution of something is done you say

19928.2 -> that we can release these resources of rather than Still

19931.4 -> establishing the connection,

19932.8 -> right which picks up some of your resources CPU resources

19936.394 -> or which takes up memory.

19938 -> So basically it's to release of the memory exception handling.

19942.4 -> So let's talk about try try block is nothing but code

19945.47 -> that could generate so suspicious could

19947.676 -> as I said that could generate an error is written

19950.5 -> into the try block.

19951.796 -> So the cache block could be

19953.607 -> more about catching a specific exception

19956.178 -> and doing something with it.

19957.958 -> So you could opt out to just break

19960.094 -> at that point or do something

19961.9 -> with it say for example want to profile an application

19965.2 -> or you want to have some instrumentation set

19967.7 -> for the application to see

19969.433 -> how much time

19970.3 -> what are the exceptions that occurring during runtime,

19972.8 -> right if you want to see

19974 -> that may be a typical way

19976 -> in which it is done is you write all this exceptions

19979.6 -> into a database

19980.9 -> and we're in later could apply some analytics to see you know,

19984.6 -> what kind of Errors have occurred in the application

19987.319 -> you could see that later on so that

19989.319 -> one of those cases

19990.378 -> where a new Let Whenever there is a particular exception you

19993.477 -> put it into a database you make an entry in the database saying

19996.766 -> that this is the exception

19998.258 -> that was caught in so-and-so time.

20000.2 -> And you could later on have some analytics to see

20003.2 -> how it could be improved

20004.4 -> how the application could be improved.

20006.5 -> So finally block is nothing but with a successful

20008.9 -> or unsuccessful the block is going to get executed

20011.6 -> as I said,

20012.1 -> this is nothing but mostly it's used to release

20015.206 -> resources such as connections and stuff like that.

20018.608 -> Let's see a demo of

20019.982 -> how we can handle exceptions to give you an example

20023.8 -> of try catch us with this was this is a suspicious code

20027.6 -> which we are running.

20028.823 -> Maybe you could put this in to try catch block and save

20031.911 -> and there is any kind of arithmetic exception

20034.5 -> that occurs just

20036 -> printing It Out Printing any kind of rhythmatic.

20040.7 -> So what we are doing here is nothing

20043.141 -> but we are catching exception

20045.1 -> and we are printing it

20046.643 -> so everything is in terms of classes

20049.1 -> again see exception itself.

20051.124 -> A class so you could click on it control click

20054.5 -> and you could see it as a class.

20056.459 -> This is source code for arithmetic exception.

20059.2 -> So you could see extends runtime exception which means

20062.472 -> arithmetic expression is a runtime exception.

20065.33 -> So it's a subclass

20066.499 -> of runtime exception you could see super

20069.052 -> and everything being used here whatever we discussed about.

20072.7 -> So arithmetic exception is nothing but it's a Constructor

20076.129 -> right and you could see super been called here.

20078.839 -> So that's how you could get

20080.403 -> into exception and you could read through it to understand

20083.441 -> how the source code is being written

20085.5 -> that would give you a good idea

20087.3 -> about how flexible Java is it's very much

20090.096 -> when it comes to flexibility

20092.092 -> and when it comes to object-oriented Paradigm,

20095.3 -> it's very much cleanly followed code

20098.1 -> so you could go

20099.1 -> and actually see at the the way the programs are being written.

20102.4 -> If you remember

20103.2 -> when you'd we did 29 by 0 the program bro,

20106.038 -> it came right from there

20107.636 -> and it didn't execute the following code.

20110.3 -> Now we have Handled it.

20111.8 -> We are saying that

20112.7 -> whenever there is an arithmetic expression

20115.403 -> in this piece of code.

20116.76 -> That's here.

20117.5 -> We are saying that

20118.415 -> whenever there is an arithmetic exception.

20120.5 -> We are going to just print it and we are going to continue it.

20123.5 -> Don't stop at that point.

20124.897 -> So you could see here

20126.105 -> the program didn't break right it give you an opportunity

20129.4 -> for you to actually handle it and it

20131.53 -> didn't break it continued.

20133.178 -> So you could see this statements been executed as well.

20136.6 -> That's why you have this results.

20138.7 -> So we had printed here.

20140.4 -> So as a part of handling exception handling,

20143.3 -> what we did is we just printed out saying that what kind

20146.762 -> of exception had occurred.

20148.4 -> So exception dot get message

20150.367 -> that gave like divide by zero this divided by 0

20153.6 -> that you see here is nothing

20155.36 -> but is printed out by this message.

20157.5 -> So it give you an opportunity

20159.291 -> to handle it and get the program running

20161.7 -> as is so try catch finally block.

20164.6 -> Basically.

20165.1 -> What I can do here is

20167.5 -> let me Define integer denominator is equal to So

20171.9 -> as I said finally block is going to execute no matter

20175.738 -> of pot is going to get executed.

20178.1 -> So I just print the message here saying I will say here.

20183.361 -> I'll put denominator

20184.9 -> when the denominator is 0 we would get exception

20187.909 -> and it would come to the exception block here

20190.858 -> or the catch block here

20192.343 -> and it would print it

20193.7 -> and then it would come to the finally block.

20196.2 -> So let me run this and see so as you could see here,

20199.7 -> it came to the exception Handler it caught arithmetic expression

20204.102 -> that is divided by 0 and then we printed out saying

20207.2 -> that printing the typical message or the actual exception

20211.1 -> that we got and it came to the finally block here.

20214.5 -> Let me put a scenario

20215.771 -> which is not going to throw exception in this case.

20218.8 -> My denominator is 1

20220.2 -> which means 29 by one we shouldn't throw any exception.

20224.1 -> So what I want to show is still it would execute

20226.9 -> the finally block

20228.033 -> so you could see here 29 been printed out

20230.7 -> which this got executed successfully this time

20233.159 -> because the denominator is not

20234.8 -> 0 it's one it got successfully executed still the finally block

20239.6 -> is been executed why to use multiple Catch blocks

20243.1 -> so you could have multiple exceptions

20245.577 -> and you could write multiple catch blocks.

20248.4 -> There are different exceptions that we spoke about it could be

20251.605 -> like a pointer exception as well which you want to handle right?

20254.871 -> So it depends

20255.491 -> upon your program logic or what you are trying to do here.

20258.441 -> So there could be null pointer exception then you have finally

20261.6 -> so you have multiple catch blocks here.

20264.1 -> So you usually don't handle null pointer exception

20267.4 -> but this is just to give you an example.

20269.694 -> So basically you have this arithmetic exception

20272.4 -> here been handled then you have null pointer exception

20275.46 -> being handled here

20276.5 -> then you have finally so

20278 -> if you want to have different exceptions to be handled

20280.776 -> within your application,

20282.036 -> you could have multiple cache blocks since all

20284.446 -> the exceptions are derived from exception catch exception.

20287.5 -> He should be placed at the end.

20289.3 -> So basically if you put the exception this exception,

20292.6 -> right if you remember the hierarchy

20294.517 -> that we spoke about all the exceptions are derived

20297.6 -> out of exception class

20299.2 -> so you could have something of this sort.

20302.1 -> So if it is

20302.9 -> not an arithmetic expression not a null pointer exception

20306.1 -> then is of course going to be some kind of exception

20309.03 -> which is going to be handled in this exception block.

20312.089 -> So basically we are catching all the exceptions

20314.6 -> here first is specific to edit mattock exception.

20317.668 -> The second one is null pointer exception

20320.127 -> if it's not a null pointer exception

20322.411 -> or arithmetic exception then this particular cache block

20325.926 -> is bound to get executed

20327.45 -> and it has to be last you cannot place it first

20330.321 -> because if you place it first this two blocks exception

20333.809 -> Handler blocks will never get executed

20336.2 -> because even this two exceptions are a subtype

20339.369 -> of exception class itself.

20341.2 -> So it has to be it is mandatory that you place it at the end

20344.691 -> or else it would be be compiled time exception

20347.457 -> so you could have something like array index

20350.1 -> out of bounds and stuff.

20351.8 -> So just to give you this is integer array.

20355.3 -> I put one two three I Define an array now

20359.5 -> I say integer array of Three elements right

20363.2 -> and if I try to access or just choose so

20366.212 -> when there are three elements the index ranges from 0 to 2.

20371.1 -> So now I put three here.

20373.2 -> So this is generic exception Handler for all the exceptions.

20377.6 -> We would have this Handler when you run it.

20380.1 -> This is going to give you a rain dicks out of bound

20382.7 -> because you are trying to access element

20385 -> at index 3 which doesn't exist.

20387.2 -> So you would see a generic exception

20389.892 -> and so it came here.

20391.8 -> What I was trying to say is

20393.5 -> so you could have arraigned X Out of bound here, right?

20396.676 -> So instead of null pointer exception now,

20399.169 -> I have arranged index out of bounds now,

20401.6 -> it would be handled by this block

20403.6 -> and it wouldn't come to the generic exception Handler.

20406.4 -> So here you saw it came to the generic exception Handler.

20409.6 -> Now what you would get is array index

20411.9 -> out of bounds exception Handler

20413.8 -> because it's been handled by this particular cache block

20417.1 -> and not the last catch block.

20418.9 -> So this one is

20419.8 -> as you go down it becomes generate.

20421.8 -> So here you could see it's been handled by array index

20424.611 -> out of bounds exception as you go down.

20426.688 -> It becomes generic more.

20428.1 -> Generally it is multiple catch block.

20430.517 -> So this is pretty much similar.

20432.6 -> We have re we have arithmetic exception

20435.6 -> that occurred array has four elements 023

20439.1 -> and you are trying to access the 10th element.

20441.4 -> That's when you would get array index out of bounds exception

20444.4 -> as we saw there could be nested try the rain.

20449 -> You could have try and inside try.

20451.318 -> So basically when you have prai inside try

20454.2 -> if there's an exception that occurs in the nested one

20457.8 -> or the innermost one,

20459.283 -> it would try to see if there's a catch Handler

20462.432 -> for that particular exception innermost one.

20465.37 -> If it doesn't find then it goes to the outer one.

20468.6 -> So in many cases it may happen

20470.5 -> that a part of the block may cause an error

20473.1 -> and the entire block may cause another such cases.

20476.409 -> You're going s to try block.

20478.3 -> So what I was trying to say is you have this one.

20482 -> We have one more like exception or shouldn't be done.

20485.7 -> So you have a nested one within this try you have one more wire.

20489.018 -> This thing with says array index which is handling

20491.901 -> null pointer exception sending just the null pointer exception.

20495.4 -> It's not handling array index out of bounds.

20498.148 -> So what I was trying to say is if such scenario occurs,

20501.508 -> it would check the innermost one

20503.5 -> if it finds the exception Handler,

20505.5 -> it would execute it.

20506.5 -> If it doesn't find then it would come to the outer one.

20509.4 -> So basically though this try doesn't have Handler

20512.819 -> for arraigned X Out of pound still it would be taken care of

20517 -> so you can see here.

20518 -> It came to the outer one.

20519.9 -> So if you would have some piece of code right after this,

20524.053 -> it won't get executed.

20525.745 -> So this piece of this code will not execute

20528.976 -> if inner try so basically

20531 -> if there's a reception which occurs in the inner block

20533.993 -> and if it's not handled it would come to the outer block

20537.1 -> but this piece of code whatever you have in between this catch

20540.717 -> and this catch would At x

20542.243 -> equal to Y to use throw keyword the Java through keyword

20545.6 -> is used to explicitly to throw an exception

20548.359 -> while executing the program.

20550.2 -> So if you want to throw something as I said,

20552.349 -> you could create your own custom exception and

20554.6 -> if you want to throw something you could throw it out you

20557.2 -> could throw an exception from your program.

20559.699 -> It can be used to throw checked or unchecked exception any kind

20563.5 -> of exception could be thrown using throws up using through

20567 -> and the Java through keyword is used inside a method

20570.493 -> so you could see here.

20572 -> Basically if B is equal to 0 you throw new exception /

20576.569 -> 0 causes an exception.

20578.4 -> So before it goes to actually dividing it by a by B,

20583 -> you are kind of handling it prior to that you are checking

20586.1 -> whether denominator is 0 if the denominator is 0

20589.2 -> you're throwing Exception by yourself, you are creating

20591.8 -> a new exception.

20592.659 -> This is kind of your own exception,

20594.559 -> right you are you're creating your own exception and saying

20597.8 -> that it's divided by 0 so for any condition

20601.036 -> so basically Denominator is equal to equal

20604 -> to 0 you could throw it from you're saying or denominator.

20608.3 -> So basically if I keep this denominator has zero

20611.5 -> and this should be prior to this just cut this

20614.8 -> and this should be done prior

20616.633 -> to this event to use throws throw this something as I said,

20620.3 -> when you have a checked exception,

20622 -> you can either handle it using prai catch

20624.6 -> or you have to throw it out of the method saying

20627.364 -> that I am not going to handle

20629.1 -> this let the collar handle it you could do

20631.58 -> that using throws keyword.

20633.15 -> The method is not taking the responsibility to handle

20636.415 -> a checked exception and it is,

20638.3 -> you know, asking the collar

20640.187 -> of the method to actually handle it.

20642.542 -> This is in terms of just checked exception

20645.3 -> when you have a checked exception.

20647.176 -> So basically since you're throwing it from there,

20650.2 -> but since you have Handler here is coming to this

20654 -> so you have this denominator you through an exception from here,

20658.064 -> but this exception is been handled here,

20660.58 -> so it came here saying That generic exception Handler.

20664 -> All right.

20664.5 -> So if I remove this

20665.8 -> that's the reason you have generic exception Handler here.

20669.1 -> So I remove this Handler I'm not going to handle

20671.9 -> exceptions whenever you throw an exception.

20674.881 -> It has to be handled

20676.232 -> since exception is a checked exception.

20678.8 -> So basically you could have run time exception

20681.6 -> which need not be handled.

20683.244 -> So basically the Handler that you see here,

20685.9 -> we just have two handlers

20687.37 -> which is for arithmetic exception and array index

20690.056 -> out of bounds exception,

20691.4 -> but we don't have a Handler for runtime exception.

20694.8 -> So that's the reason it gave you an error

20697.3 -> saying denominator is 0 so,

20699.1 -> this is an exception that we through here using throws.

20702.4 -> So it's giving you an error right here

20704.441 -> because this is a checked exception.

20706.394 -> The exception itself is is a checked exception.

20709.105 -> Now, you could either handle it

20710.939 -> like the way we had handled it here.

20713.033 -> You could write catch exception and you could handle the way

20716.704 -> you want to so you have two options now

20719.008 -> when you get into this scenario into this situation,

20722.1 -> You have two ways to handle it either right exception

20725.803 -> and handle it.

20726.8 -> This would be a Handler.

20728.2 -> If you see the compilation error has gone or this is one thing

20731.7 -> that you could do or the other thing

20733.6 -> that you could do is you could ask this method

20737.012 -> this method can say I'm not going to handle it.

20740.5 -> I'm going to throw it for my collar to handle it.

20743.9 -> So the main method is saying I am not going to handle it.

20747.506 -> I'm just throwing it off from my side from my code

20750.718 -> or the caller to handle it.

20752.416 -> So see the exception has again the error has gone.

20755.5 -> So basically Whenever there is a checked exception

20757.768 -> you have to option

20758.633 -> and this is happening at the compile time,

20760.683 -> by the way, so you have to ensure

20762.4 -> that you either handle it or you throw it throw

20764.817 -> in the sense throws its through throws me anything

20767.7 -> that I am not going to handle this at the collar handle him

20770.7 -> as you could see

20771.735 -> the throws keyword was added in the method signature.

20775.1 -> We saw how we Throw exception.

20777.159 -> We throw exception from here you check

20779.7 -> for some condition you throw exception

20781.7 -> from Why uvu's throws throw is basically to throw an exception

20786.3 -> and a method saying

20787.6 -> that I am not going to handle the exception.

20790.004 -> So what's the difference between through and throws

20792.8 -> the throw keyword is used to explicitly throw an exception.

20795.7 -> The throws keyword is used to declare an exception.

20798.9 -> The through keyword is followed by an instance.

20802.176 -> The throws keyword is followed by throwable class.

20805.686 -> Alright, so here you could see this is throws

20808.699 -> keyword is actually

20810 -> by instance you create an instance of exception.

20812.8 -> Whereas throws is the class

20814.432 -> itself through keyword is used within a method

20817.154 -> and throws keyword is used with the method signature.

20820.3 -> So you could see through is used within a method

20823.581 -> within the method body

20825.054 -> and you could see throws at the signature level.

20828.441 -> So you have throws

20829.694 -> and throw so throw is nothing but whenever you want to check

20833.8 -> whether there is an exception and you want to throw it out

20836.6 -> you want to actually trigger the exception that's

20839.2 -> when you would right through and you would This exception.

20842.3 -> So basically here we are checking for a condition

20844.7 -> if denominator is equal to zero,

20846.3 -> which is potentially

20847.3 -> which would cause error further down the line.

20850.455 -> So we are checking it up front saying

20852.9 -> that if the denominator is 0

20854.69 -> then we are not passing it further write in such scenarios.

20858.4 -> We could throw the exception right away.

20860.7 -> That's how you figure the exception from the program

20863.898 -> Rose is nothing but it's at the signature level

20866.767 -> of the method

20867.577 -> that you could see

20868.7 -> and what you mention out by throws this

20872 -> that main is saying here

20873.4 -> that I'm not going to handle the exception

20875.507 -> and just going to throw it off.

20877.1 -> So this are unchecked exceptions, by the way.

20879.7 -> So whatever is not been handled here

20882 -> if there's some exception handled here it would get

20884.5 -> to the exception Handler or the catch block.

20887 -> But if there is something

20888.2 -> that is not been handled here would be thrown

20890.4 -> out of this main method main method won't handle it.

20893.4 -> That's the reason why we have throws

20895.733 -> through keyword is used within the method

20898.4 -> and throws keyword is used with the method signature.

20902 -> Through keyword can throw only one exception

20905.262 -> whereas throws keyword can be used to declare

20908.57 -> multiple exception.

20910 -> Basically, you could have

20911.5 -> something like this one exception say ioexception

20914.8 -> so you could have multiple exceptions here.

20917.247 -> So the main is saying I'm not going to handle ioexception.

20920.642 -> I'm not going to handle exception or something of that

20923.8 -> so you could have multiple exceptions after throws

20927.2 -> user-defined exceptions.

20929 -> You can create your own exception and it is called

20931.629 -> as user-defined exception

20933.1 -> or custom exceptions user-defined exception class

20937.133 -> can be created by creating a class child class of exception.

20941.6 -> So basically create exception.

20943.907 -> I create a clasp which is SE custom exception.

20947.369 -> Now, this custom exception is extending exception

20951.1 -> so you could have your own classes defined

20953.9 -> and it would have like this.

20956.1 -> So what you exception

20957.455 -> you get you go you could pass that exception directly here.

20961.2 -> So this is See,

20962.171 -> what I'm trying to do here is overloading of Constructor.

20965.8 -> So you could see if you are passing string.

20968.288 -> It would come to this.

20969.588 -> If you are passing exception to come to this Constructor.

20973.2 -> So you could create your own exception here.

20976.093 -> So basically to give you example of this instead of exception.

20980.2 -> What I throw is I can have a new custom exception.

20984.2 -> So initially I was throwing exception.

20986.364 -> Now what I am saying is new custom exception.

20989.022 -> This is the exception that I have created.

20991.5 -> It's my own exception when I run this now,

20994.464 -> you can see that it should throw custom exception

20997.603 -> so you can see here exception

20999.524 -> in thread main thread main is nothing but your main method

21003.3 -> where your program is executing and it shows the exception type

21007.5 -> which is custom exception which is created by me

21010.5 -> and I have passed the strings in the denominator is 0

21013.8 -> and at what point

21014.9 -> or at which line this particular exception occurred can see it

21018.6 -> in the stack trace.

21019.792 -> This is a stack Trace basically.

21021.8 -> Whatever you get here

21023.112 -> when an exception occurs is nothing but stack Trace.

21027.1 -> So hi everyone,

21028.115 -> welcome to module number four before I start off L.

21031.9 -> Just briefed on what we covered in module number 3,

21035.1 -> so we covered on Hoops Concepts in general.

21038.2 -> What are the Hoops Concepts

21039.665 -> what are different concepts or terminologies

21042 -> that we have in oops?

21043.5 -> Then we saw how Java is aligned to those Hoops Concepts

21047.4 -> how Java is known as object oriented program,

21050.9 -> right or how Java is aligned to object

21053.6 -> oriented programming Paradigm.

21055.8 -> Then we spoke about abstract classes,

21058 -> which is a different modifier all together,

21060.2 -> right and then we spoke about a hundred percent abstraction,

21063.376 -> which is nothing but interface which is a construct in Java

21066.5 -> which helps you to specify something

21068.8 -> and you could have different implementations as

21071.7 -> per the specifications

21073.2 -> then we spoke about exception, right?

21075.8 -> What are different exceptions

21077.7 -> and why do we have exceptions at all?

21080.1 -> And how do we catch exceptions

21082.2 -> or what is the need to catch exception

21084.6 -> and what are different types of exceptions right?

21087.1 -> Have like checked unchecked exceptions checked exception has

21090.536 -> to be caught by your application

21092.4 -> or a particular method my top to just throw it off rather than

21096.4 -> actually handling it through the throws keyword, right?

21099.74 -> We touch base on regular expression as well.

21102.4 -> And why do we need regular expression and

21105.006 -> what are different classes

21106.7 -> that Java has to support regular expression?

21110.3 -> Alright.

21110.7 -> So today we would be covering file handling

21113.691 -> and Java Collections framework.

21115.9 -> All right.

21116.4 -> So file handling is nothing

21118 -> but you have external files you might have something

21121.245 -> on your network

21122.2 -> or it could be

21122.9 -> on your local machine itself and you want to access it

21125.938 -> and do something on it

21127.2 -> or you might want to have data

21128.98 -> that's been coming to your program.

21130.923 -> You might want to write it into a file

21133.1 -> so that you could kind of analyze it later.

21135.637 -> I spoke about exception right?

21137.45 -> If you get an exception,

21138.9 -> you could write it into a file

21140.4 -> so that you could later on go through it

21142.497 -> and understand at what time a particular exception occurred

21145.7 -> and you could act upon it.

21147.2 -> It's a kind of profiling

21148.673 -> and instrumentation turn on application to understand more

21152.3 -> on the behavior of the application

21154.4 -> and to improvise on it.

21156.1 -> Such activities could be done using file handling

21159.2 -> will talk about Java Collections framework.

21161.68 -> Java Collections framework is nothing but you have

21164.6 -> a re array list and everything.

21166.467 -> That is we spoke about arrays in the previous topics.

21169.6 -> But Java Collections framework itself exposes array list,

21173.17 -> which is a dynamic list.

21174.5 -> You don't have to manage it.

21175.9 -> So remember in list we said

21177.745 -> that when you take Claire a list or declare an array,

21181.4 -> you have to mention the size of it

21183.599 -> whereas array list is dynamic.

21185.6 -> You don't have to mention it.

21187.176 -> It keeps growing.

21188.2 -> So these are the topics

21189.4 -> that we are going to cover file input output of operation

21192.2 -> in Java wrapper classes in Java.

21194.7 -> We are going to talk about Java collection Frameworks.

21197.5 -> We are going to talk about list and its classification in Java Q

21201.7 -> in Java and sets and their classification in Java.

21205.2 -> So as you could relate all this Action all this components

21208.6 -> within the collection Frameworks are nothing

21210.7 -> but data structures in general.

21212.284 -> That's you straight.

21213.46 -> So maybe in see you might have used different data structure

21216.5 -> and whereas in different languages,

21218.135 -> you have different data structures, right?

21220 -> This is just to handle data data structures are nothing

21222.7 -> but to store data efficiently

21224.7 -> and you could select one of them based on the use cases

21227.62 -> that you're handling within your application.

21230.1 -> So let's start with file I/O file

21232.4 -> I/ O is nothing

21233.308 -> but you have a file on your disk and if you want to do something

21237.123 -> if you want to write to that or

21239 -> if you want to read from that file,

21240.9 -> you would ideally use file I/O API.

21243.8 -> All right.

21244.716 -> So file I/O is used to process the input

21247.8 -> and produce output for a specific file.

21250.5 -> All right, so you could access some file

21252.7 -> within your local disk do something

21254.8 -> and you can write it on to a different file as well.

21258.3 -> Write Java dot IO package

21260.6 -> contains all the classes required for input

21263.764 -> and output operation for a Phi.

21266.1 -> All right,

21266.9 -> so As we said package is nothing but namespacing right?

21270.5 -> So everything is grouped.

21272.431 -> All the I/O classes are all the classes in Java

21276 -> that is handling.

21277.3 -> IO is grouped into Java dot IO package.

21280.3 -> Okay, that makes it easier

21281.995 -> for programmers to understand as well.

21284.408 -> Right?

21284.8 -> So if you're doing a lot of I/O operations,

21286.9 -> you could directly say import Java dot IO dot star

21290.126 -> which would in put all the classes

21292.3 -> within your Java dot IO package.

21294.6 -> All right, the files can be text file or it

21297.823 -> could be binary file, right

21299.9 -> so you could imagine not always you deal with a text file,

21303.971 -> right you have other files as well.

21306.4 -> So nowadays.

21307.4 -> There's a lot of things going on

21309.3 -> on iot right internet of things.

21311.4 -> So you get data from different systems.

21313.8 -> It could be like your mobile phones.

21315.8 -> It could be from the car sensors or elsewhere, right?

21318.9 -> You have a real-time raw information coming in

21321.919 -> into your system for analytics.

21324 -> So such data cannot be a text file.

21326.8 -> Txt file as such is a heavy file,

21329.3 -> right so such iot applications.

21331.7 -> What is been passed between systems our intercommunication

21335.246 -> between systems is done through a binary file,

21338.055 -> which is kind of lightweight right

21340.028 -> compared to text file txt files are heavier.

21342.7 -> So you could imagine this files not being just the text file.

21345.8 -> It could be binary files and so on when I say binary files,

21348.7 -> it could be it could be images

21350.7 -> as well write different images

21352.7 -> that could be shared among system or some image

21356.2 -> that is there on your local disk,

21357.8 -> which you want to read into Java

21359.4 -> and do something on it some kind of graphical processing

21362.6 -> on it right stream is a sequence of data.

21365.267 -> So you convert this file

21366.866 -> into a stream and you use it with in Java.

21369.6 -> Okay, we'll look at example,

21371.5 -> which would give you a clear idea of what I'm talking about.

21375.14 -> Okay, so here you can see an example

21377.252 -> where in you have a file

21378.7 -> which is student dot txt into your local system

21381.807 -> into your local disk

21383.1 -> where you are running this program right then you

21386.2 -> have a pretty Traitor

21387.37 -> this is nothing but a printwriter is a class

21389.93 -> that is exposed by Java

21391.341 -> which is there

21392.2 -> in Java dot IO package you would pass on this file.

21395.387 -> So initially you have new file

21397.3 -> and you pass on the path of this file

21399.393 -> that you are going to read or do operations

21401.872 -> on not just read it could be right operations as well.

21405 -> So basically you have new file

21407.158 -> and you specify the path name or initialize the file.

21411.2 -> The next thing that you do is you have printwriter wherein

21415.024 -> you pass this file.

21416.22 -> All right.

21417 -> Now what we are trying to do here is we are trying to write

21420.7 -> into a Phi, right?

21421.915 -> We are trying to write the name or the some ID or something.

21425.9 -> We're trying to write this content into a Phi right

21429.5 -> into your local file will write a program on this

21432.64 -> which would give you a clear idea and the next step

21435.6 -> that we are doing here is kind of we are reading it from a Phi.

21439.229 -> Alright.

21439.7 -> So the first step

21440.593 -> that you do is write it into a file The Next Step

21443.278 -> that you do is read from the same file

21445.294 -> and print the contents of it.

21447 -> All right, so it's not mandatory

21448.882 -> that you have to specify the same file for reading right?

21452 -> This is for just for the convenience

21453.944 -> or just to demo it.

21455 -> We are using the same file you could have

21457 -> different file as well.

21458.3 -> All right, so let me show you how this is done.

21462 -> So again, I create a new project for today,

21464.9 -> which is All right,

21469.8 -> so we create a new project and Eureka.

21475.9 -> module 4 Alright, so we have this project now.

21483.158 -> Let's create a new class.

21486.1 -> Calm down daddy.

21486.9 -> Rekha is nothing but the package name

21489.7 -> and I give up.

21495.2 -> input output demo Alright,

21498.1 -> so before we start off I can do one thing.

21502.9 -> I can create a folder here.

21505.3 -> Say said, Eureka.

21509.8 -> All right, so we'll put all the files here.

21512.5 -> So this is the empty folder

21514.3 -> that I have created right now or let me put it here.

21520.5 -> So for Simplicity,

21521.837 -> I'm going to put it on C drive itself.

21524.505 -> Alright, so on see have created a director IO directory

21528.4 -> where in we are going to dump all the files, right?

21530.819 -> Whatever we are going to do is going to come

21532.9 -> into this particular directory.

21534.8 -> Alright.

21535.2 -> So the first thing

21536.2 -> that we are going to do is so now we are thinking of writing

21540.251 -> into a file first right?

21541.9 -> So I create a main method right?

21544.361 -> The first thing that I do is create a file.

21549 -> All right, and I create a new file.

21552.3 -> Which is nothing,

21553.3 -> but I am calling the Constructor of a class of the class file,

21556.661 -> which is with in Java.

21557.8 -> Right?

21558.3 -> It's not something that we are writing.

21560.3 -> So Java itself has this internal file class,

21563.317 -> which is file.

21564.357 -> All right.

21565.1 -> So now a point to this particular directory.

21568.9 -> All right, calm down Ed Eureka IO and we say

21576.4 -> so I call it as employee info dot txt.

21579.7 -> Alright, so we are going to write into this file now

21582.699 -> from java program.

21583.681 -> So now it's showing up an error saying

21585.7 -> that which file I want to refer to

21588.238 -> as we said the all the I/O related files

21591.3 -> all the all the I/O related classes are placed

21594.2 -> in Java dot IO package.

21595.9 -> So I select this package

21597.424 -> once selected you can see an import statement here.

21601.4 -> Being up.

21601.9 -> So why do we have input statement

21603.8 -> because file is a class

21606 -> which resides in a different package then calm down

21609.152 -> Eureka had it been within calm down Eureka.

21611.8 -> You need not import it it's outside.

21614.396 -> So you have to put it right

21616.5 -> then there are different ways in which you could write it,

21619.3 -> but now we'll follow the same example.

21622.1 -> So I write printwriter printwriter.

21625.2 -> Is there within Java dot IO

21627.3 -> and you could see it imported here.

21629.9 -> All right employ info writers if example,

21635.5 -> okay now we create

21636.811 -> a new printwriter and if you see the Constructor of printwriter,

21641.4 -> so we spoke about Constructor overloading and stuff like that.

21645.405 -> Right?

21645.8 -> So you could see if you go into the source code.

21649.084 -> If you want to Deep dive more you could go

21651.6 -> into the source code and see it takes file.

21654.4 -> Alright, so here you could see an option

21656.917 -> which is nothing but it consumes file.

21659.305 -> So the file which we created above.

21661.9 -> I can put it as e employ info file.

21668.8 -> All right.

21669.523 -> So there's a file that's created here.

21671.7 -> So I put the same file here right

21674.7 -> since the Constructor supports file itself.

21677.5 -> Now this is checked exception.

21679.541 -> All right, you could see here.

21681.493 -> It is saying Java is explicitly saying

21683.947 -> that you are not handling this exception.

21686.6 -> All right.

21687.3 -> So ideally the better practice

21689.1 -> is we shouldn't be writing everything into the main

21691.771 -> because it would become cumbersome to understand

21694.316 -> later on right you shouldn't be dumping everything

21696.973 -> to the main method.

21698.07 -> So as a good practice,

21699.437 -> what you should do is you should create

21701.8 -> a new method right to file.

21705.7 -> All right.

21706.404 -> So this is best practices, right?

21708.6 -> It's not mandatory.

21709.8 -> Java is not going to tell you there is an error or something.

21713.1 -> But as a part of best practices,

21715.2 -> this is how you should write programs

21717.4 -> which would make it readable for others

21719.5 -> because tomorrow some other developer is going to handle

21722.1 -> this particular class.

21723.109 -> It's not that you have going to be there

21724.9 -> throughout right so basically

21726.529 -> so that other developers can easily read It

21729.042 -> and maintain it.

21730 -> Well, this is how we write it.

21732.6 -> I move this content.

21734.1 -> Whatever the writing part is.

21736.194 -> I move this content here.

21738.1 -> Alright, so now it's showing up an error saying

21741.3 -> that it's not been handled right file not found exception

21745.1 -> is not been handled because it's a checked exception.

21748.6 -> So remember in the checked exception we said

21751.14 -> that there are two options one is to handle it

21753.8 -> within your method all this right to file method

21756.851 -> can hop to throw it off saying

21758.8 -> that I am not going to handle it let the caller handle it.

21761.9 -> So when I say caller caller is nothing but this method alright,

21766.1 -> so I am going to create say here input demo.

21771.934 -> Sam trading in instance here.

21774.2 -> Alright and demoed right to file and I'm going to pass the file

21778.859 -> that we created here.

21780.3 -> All right, so there was one file that we created here

21783.382 -> which is pointing to an employee info Dot txt.

21786.873 -> And we are calling this method to write it

21790.5 -> if you think about the reusability part of it.

21793.5 -> So this is how you make the method reusable.

21796.5 -> If you put it into Maine you cannot reuse it.

21799.4 -> If you're taking the right logic outside the main and refactoring

21802.7 -> and putting all the code

21803.9 -> that is specific to writing to a file do particular method.

21808.1 -> You could reuse this method you're making

21810.1 -> it generic right now.

21811.9 -> I opted to throw it off or let's handle it.

21815.9 -> All right when I say let's handle it.

21818.424 -> It's nothing but you have try catch block.

21821.3 -> All right, so I say Catch so what exception was that?

21826.1 -> It was filenotfoundexception.

21827.964 -> So you need to have file already in place.

21831.1 -> Alright, so here I print saying

21833.8 -> that given file was not found on the local disk.

21839.2 -> All right, and once that file Maybe we can print the name

21844.057 -> of the file as well.

21847 -> Alright, so here we have chosen to handle it.

21850.4 -> Okay, so we remove this.

21852.2 -> Alright, so we have

21853.6 -> a try catch block written now and we say that Okay,

21859.5 -> so we are handling this error.

21861.8 -> So we say that it just print a message saying

21864.9 -> that given file was not found on the local disk.

21868.5 -> And as a good practice,

21869.9 -> I don't want further processing right

21872.068 -> if I don't have a file I don't want to process it further.

21875.7 -> So I say through runtime exception

21879.2 -> and I so runtime exception is unchecked exception.

21883 -> It won't give you error even if you don't handle it,

21886.2 -> right whereas this was a checked exception.

21888.81 -> That's why you are getting error.

21890.8 -> Basically.

21891.372 -> What I'm doing is I'm catching the checked exception

21894.372 -> and wrapping it into unchecked exception.

21896.7 -> All right, because I don't want this to be processed further.

21900.864 -> So once we have this printwriter set,

21903.6 -> so I'll have to take this print right outside

21905.8 -> or I'll get here.

21907.2 -> Alright, so what I do is employ Dot println

21910.6 -> and I write some content

21912.4 -> to it and say in this case I am writing vinod.

21920.1 -> I write some ID to it as well.

21924 -> Anything you could write.

21925.7 -> Okay one side right into the file.

21928.588 -> I have to ensure that I close the file.

21932.1 -> So basically you could have finally block

21935.7 -> so you would do this.

21937.576 -> I'll have to take so this

21939.46 -> if this is within try so it's not accessible

21942.8 -> within the finally block.

21944.6 -> So to make it accessible

21946.239 -> what you will have to do is you'll have to take it outside.

21951.9 -> All right.

21952.4 -> So I Define it outside Dry block

21955.707 -> so that it gets accessed in finally.

21958.4 -> Alright, so now

21959.553 -> what I do is employ info dot writer Dot close

21963.4 -> I close it.

21964.2 -> So that's one of the use cases of finally as I said,

21967.899 -> it's basically for closing the resources.

21971.1 -> So this finally would execute even

21973.8 -> if this doesn't throw

21975.14 -> or don't throw any exception and it would get executed even

21979.141 -> if it throws an exception.

21981 -> All right, so

21982.1 -> that's what the use of finally block is.

21985.2 -> So let me quickly run this program to see I have

21988.6 -> to create a file here.

21992.7 -> If I create a text file here Dot txt.

21996.9 -> All right before I create a file

21998.871 -> maybe I will I would want to show you what happens

22001.89 -> if we don't have a file, right?

22004 -> So if you don't have a file I run it

22006.515 -> so we don't have anything in to see at Eureka

22009.9 -> I oh, all right.

22013.4 -> Basically, you're trying to write into a file

22015.6 -> which doesn't exist at all.

22018.896 -> So it's building.

22021.392 -> And it's running now.

22024.3 -> Even if you don't have a file,

22026.29 -> it doesn't throw file not found exception rather.

22029.475 -> It creates one on its own.

22031.2 -> So remember we didn't have anything here.

22033.6 -> Now.

22033.8 -> Let's see the content of this file.

22035.9 -> You could see whatever we rode right the employee name

22039.3 -> and you could see the employee ID,

22041.742 -> which is hundred.

22043.9 -> So whatever you wrote here came into that file.

22046.846 -> All right.

22047.486 -> Now, let's write a program to scan

22049.8 -> or read through this file.

22052.169 -> All right, so maybe I can use the same file

22055.4 -> or I can use something like All right.

22058.9 -> So I write something like BMW cities howdy.

22063.8 -> All right, I I write something like this.

22066.4 -> It's a vehicle info and say

22068.9 -> you have something like let's keep it

22071.499 -> as is okay.

22072.3 -> So you have vehicle info in here.

22076.1 -> So now we are writing a program to read from a file.

22080.3 -> All right, so we pass on the file parameter here.

22083.123 -> There are different ways in which you can do.

22085.9 -> All right, so we create scanner now scanner takes

22090.6 -> if you see instructor you could see that scanner takes

22094.665 -> file as a parameter.

22096.2 -> All right.

22096.963 -> So I put scanner file again.

22099.1 -> It is saying

22099.865 -> that file not found exception is to be handled.

22102.8 -> So in this case,

22103.935 -> you have to be sure the file is present, right,

22107.6 -> since you are reading the file the earlier case

22109.9 -> it was writing to the file

22111.2 -> which can create a file

22112.259 -> but reading to the file you have to be sure

22114.359 -> that the file is present

22115.5 -> or else you would get a file not found exception.

22119.1 -> So in this case, I choose to throw the exception.

22123.6 -> The read file is saying

22125.133 -> that I don't want to handle this exception i

22128 -> instead threw it off.

22129.401 -> All right, you could see throws here.

22132.1 -> Okay.

22132.8 -> Now what we do is we read lines from it, right?

22136.6 -> So we have like Okay,

22142.502 -> so we read line from it and we just print it out.

22147.1 -> basically, you would have something like So let

22152.3 -> me just print line read from the input file, right?

22157.3 -> So this is nothing

22158.302 -> but we are just printing whatever we read from there.

22161.4 -> Basically, this should have something like it should Loop in

22165.2 -> until it's end of the file.

22169 -> Alright, so this is

22170.162 -> how you use the while loop similar to what you do

22173.4 -> in C and C++ right till the end

22175.431 -> of the file till yo F character

22177.463 -> is encountered you kind of read the Lines within the file.

22181.6 -> All right.

22182.095 -> So this is a method

22183.095 -> that we have written but we haven't invoked this method yet.

22186.2 -> So I create file

22187.3 -> since it's a different file we have to create

22190.2 -> a file vehicle info is equal to new file.

22194.4 -> We give the path of it,

22196 -> which is nothing but a Eureka IO vehicle info dot txt.

22202.1 -> All right, we created a file here.

22205.199 -> Now, what we are going to do is we are going to call

22208.3 -> read file on this file

22210.1 -> or vehicle info file

22212 -> and we should be able to see the contents of it.

22214.9 -> All right.

22215.4 -> So now one thing here is

22217.031 -> since you have thrown exception it's saying

22219.885 -> that exception has to be handled here.

22222.315 -> All right, I can choose to not handle the exception

22225.6 -> here as well and I am adding it to the method signature.

22229.1 -> Sure, so main would throw as well.

22231.2 -> So basically what would happen is

22233.082 -> if you don't have a file

22234.287 -> which is being read your program would stop at that point

22237.149 -> because you're not handling it anywhere, right?

22239.5 -> You're just throwing it off up the ladder.

22241.8 -> So basically at the end

22243.1 -> if you don't have a file you're going to get

22245.4 -> an exception your program is going to stop there.

22249.123 -> I run this file and let's see what we get.

22254.4 -> All right, so you could see BMW Mercedes

22257.4 -> and Audi being read out from vehicle info.

22260.9 -> This was the content that we had within the file

22263.388 -> and which you could see it's been bred.

22266.5 -> So file writer and file reader

22269 -> so similar to print this one is a different way of writing it.

22273.3 -> So what's written within this program is nothing

22275.923 -> but we create an instance of file writer

22278.1 -> and we pass the string the path of the file rather as an input

22282.513 -> to the file writer now file writer

22285.6 -> is nothing but it's character-oriented

22287.873 -> right print was not as such character oriented.

22290.7 -> This one is character oriented

22292.2 -> which means two bites right character is nothing

22294.7 -> but two bite-sized with in Java.

22297.1 -> So this one is not like it doesn't work

22300.105 -> at the byte level.

22302.1 -> Basically, whenever

22303.264 -> you're dealing with character-oriented file,

22305.9 -> you could use this one rather than printwriter.

22309 -> All right, objectify lighter is being created

22312.034 -> which is a character oriented file or which is

22315.012 -> a character oriented place.

22316.8 -> All right, and you write to a file you're writing

22319.975 -> to the file here.

22321.2 -> All right, and similarly when you use file reader,

22324.269 -> it's a character oriented reader reads character one character

22328.058 -> at a time from the file that you have mentioned here.

22331.7 -> So maybe I will take just an example of writing it

22335.1 -> because it's going to be pretty much similar.

22343.4 -> So quickly write this program.

22345.512 -> You have a main method you create a method

22348.485 -> to say you have public or it could be a private method

22352.2 -> as I said,

22352.825 -> the best practice would be to restrict

22355.1 -> as much as possible rate.

22356.506 -> If you don't want this method to be called from outside,

22359.6 -> you could have private method

22361.7 -> so it's going to be right to file.

22365.6 -> So you need to give string or you can have file as well.

22369.826 -> Whatever you prefer to would have file

22373 -> and file to write to okay.

22376.8 -> So basically we were talking about file right?

22380.1 -> All right, so I create file right to object.

22383.5 -> Okay, and again say it's a bike info.

22389.553 -> And I pause this file to which you have to write.

22394.5 -> All right.

22395.299 -> So again, you could see now you could see a checked exception

22398.6 -> that is nothing but issuing that ioexception has

22401.979 -> to be handled now I choose to throw it off.

22405.8 -> I'm not handling it here.

22408.45 -> Bike in four thought I write to the file

22412.7 -> and I write some content.

22416.1 -> Basically, this should be writer just to make it more elaborate.

22420.3 -> All right, I say right Road close close

22423.5 -> this particular file.

22425.009 -> Okay.

22425.394 -> Now I give a call to this method

22428.4 -> which is nothing but file writer demo is equal

22431.1 -> to Nu we are creating instance of it.

22433.6 -> Okay, let me create a file

22435.8 -> which is nothing but file bike info file

22441.4 -> and which is new file and within the same directory,

22446.407 -> which is nothing but calm dot Ed u--

22449.1 -> record at I/O.

22451.2 -> I create by info Dot txt.

22454.6 -> Alright, so what we are doing here is using file writer.

22457.57 -> We are going to write into biking for DOT txt.

22460.023 -> And we are going to write this content

22462.2 -> that is Ducati and maybe

22463.767 -> after this we could have whatever you have in buffer

22468.1 -> that that would be flushed off to or disc.

22473.2 -> Alright, so when I run this basically we

22475.787 -> don't have a file now bike info and I think it should create it

22480.2 -> so you could see here.

22481.569 -> We don't have a bike info file.

22484.615 -> Okay.

22485 -> So again, let me talk about this program.

22487.666 -> So what we have written is we have a file.

22490.4 -> So what we are trying to do is we are earlier the program

22493.976 -> we wrote using printwriter.

22495.7 -> Now we are going to use five writer which is

22498.3 -> a character stream based I/ O so we are going to write

22501.5 -> into bike info dot txt file

22503.7 -> and we have a method right to file

22506.34 -> in which we are creating a file writer object

22509.738 -> which is taking up this parameter

22512.115 -> or taking this pile,

22513.6 -> which we are going to read through as the input.

22516.5 -> All right and not read through its rather, right?

22519.6 -> So the file to which we are going to write

22522.033 -> is taken as an input parameter

22523.85 -> to the file writer and we are writing into this file.

22527 -> So right now we are just writing to cart either.

22530 -> All right.

22530.6 -> So I invoke this method like file writer demo dot right

22536.2 -> to file and I pass on this file here.

22540.169 -> All right shows up an error that you have to handle iOS.

22544.4 -> Option which is been thrown from right to file.

22547.7 -> So I choose not to handle it here as well.

22550.8 -> Which means if you don't have that file

22553.6 -> or if there's some ioexception

22555.512 -> that's been triggered you would program would stop.

22558.719 -> All right, so I run this program.

22562.6 -> So basically, it should create file

22564.848 -> and should write to it as well.

22566.9 -> All right, so I go to the directory.

22569.1 -> So you see bike info file has been created here.

22572.19 -> We didn't have it earlier.

22574.1 -> It got created after we ran this program now,

22577.4 -> I just open it up

22578.5 -> and you should see the value Ducati been written there.

22581.9 -> All right, so that's about file writer

22583.812 -> and similar to that.

22584.874 -> You have to just read through it.

22586.598 -> You have to pass the file

22588.068 -> that you want to read as a parameter

22589.992 -> and you just have while loop to iterate through

22592.5 -> till the end of the file and you can print the character.

22595.5 -> So basically it's pretty much similar to what we did

22597.7 -> for the printwriter,

22598.8 -> but I just wanted to demo for one of these cases

22602.635 -> so we took an example of why writer.

22605.669 -> Alright, so now let's move towards stream stream based I /O

22610.2 -> so Java streams are used to perform input

22613.105 -> and output operations on eight bits.

22615.739 -> A bite right screams is basically operating

22618.9 -> on a bite input stream.

22620.8 -> It is used to read the data

22622.241 -> from The Source it could be file it could be keyboard

22625.477 -> or it could be anywhere across across the network,

22628.5 -> right?

22628.859 -> It could be a socket as well.

22630.6 -> So basically it is used to read the data from the source

22634.2 -> that is input stream and output stream is nothing but

22637.9 -> if you want to write something from your program

22640.7 -> to any resource on a network,

22642.9 -> that would be nothing but write

22645.1 -> that would be nothing but output stream.

22647.8 -> All right.

22648.3 -> So with output stream you would typically write data

22651.508 -> to a destination and with input stream.

22654.1 -> You're going to read it from a source.

22656.4 -> All right, just to walk you through so we have object

22660.3 -> as I said all classes

22662.4 -> or every class in Java is inherited from a class.

22666.4 -> That is object.

22667.6 -> All right.

22668.364 -> This is a super class

22669.6 -> for all the objects all the classes in Java.

22673.1 -> Okay.

22673.7 -> So you have object and you you could see

22676.612 -> that this input stream and output stream.

22679.6 -> So let's talk about the input stream.

22681.582 -> There's file input.

22682.7 -> Beam, there's byte array input stream this filter input stream

22687 -> and this object input stream.

22688.9 -> So we'll talk about this in the coming slides.

22691.265 -> Why do we have object input stream

22693 -> and stuff like that.

22694.1 -> But right now you could imagine

22695.8 -> that we have multiple classes or you could think

22698.338 -> that there are multiple classes with it input stream,

22701.147 -> which are used for different use cases.

22703.2 -> Like you have buffered input stream,

22705.258 -> which is nothing but it buffers it.

22707.2 -> It doesn't read or write it in one go.

22709.47 -> It's sort of buffers it and then it flushes it over.

22712.7 -> All right output stream similar to input stream.

22715.5 -> We have an output stream.

22717.016 -> It's an interface.

22718.165 -> I believe which has got several implementations

22721.1 -> like file output stream.

22722.91 -> You have byte array output stream.

22725.4 -> You have filter output stream.

22727.427 -> You have object output stream

22729.462 -> and filter output stream is further categorized as

22733 -> or has further sub classes as buffered output stream

22737.6 -> and data output stream.

22739.5 -> All right, so in further slides,

22740.95 -> we are going to discuss

22742.1 -> file input Stream file output stream object input stream

22746.087 -> and object output stream.

22748.1 -> Okay, so file output stream class

22750.4 -> and file input stream class.

22752.131 -> Let's talk about it.

22753.451 -> The file output stream class

22755.3 -> is used to write to a file right you

22757.6 -> you could take a bite array and you could write to a Phi.

22761.3 -> All right, so you could take something.

22763.3 -> If you have a string you could convert it

22765.3 -> into a byte array and you could pass it

22767.2 -> and it would write to a file.

22769.298 -> So remember we said it's a byte oriented, right?

22773.1 -> So basically it's going to write take array as input

22777.6 -> and it's going to write to it

22779.472 -> write to the file that you have mentioned in there.

22782.7 -> Right so you could take integer as well.

22785.6 -> It is used to write the specified bite

22788.3 -> to the file output stream.

22790.103 -> So you could provide integer as well.

22792.8 -> There's a close method which is nothing

22795.302 -> but closing the Stream So streams are nothing

22798.2 -> but it is hooked up to the resources.

22800.388 -> It is taking up resources

22801.955 -> and there is a Action between your program

22804.442 -> and the file established rate when you create three times.

22807.9 -> So when you close it you close that connection and it is free

22811.429 -> for garbage collector

22812.8 -> to remove that particular object from memory.

22816.2 -> So basically freeze memory as well right

22819.1 -> unless you close it.

22820.4 -> It's going to stay in the memory.

22822.1 -> So it's a good practice to close it right

22824.877 -> after you use it.

22826.068 -> Okay rights, you could write to a particular offset,

22829.754 -> which could be done using right method.

22832.5 -> So right length bites,

22834.6 -> whatever length you have mentioned in as third argument,

22837.647 -> it would write it to a particular offset.

22840 -> It would write the bite that you have even

22842.4 -> or bite that you have passed in as input.

22845.2 -> It would write that bite do

22847.4 -> a particular Offset you have flush method,

22850.7 -> which is nothing but flushes the output stream

22853.4 -> and forces any buffered output bytes to be written out.

22857.036 -> All right, so it could be buffered as I said,

22860 -> so not writing it each

22861.8 -> and every time You have bite basically it buffers it

22865.1 -> and you could have flush method to flush it off to the Phi.

22869.3 -> So basically we have buffered stream,

22872.3 -> which is this Method All right.

22874.961 -> So here we have file output stream

22877.5 -> and using file output stream.

22879.505 -> We rewrite it to the file and then we close the file.

22883.4 -> All right, as far as the syntax is concerned.

22885.988 -> It's pretty much similar to file writer example

22888.8 -> that we took but just to give you a demo just to show you

22893 -> how it is.

22893.9 -> We'll have fun demo done here.

22896.7 -> All right, so I create a new class

22899.1 -> which is nothing but file output stream demo.

22907.1 -> Alright, so we have a main method

22910.4 -> and I create a new method

22913.361 -> which is like file write to a file.

22917.5 -> Which could be like private method

22919.934 -> private void write to a file?

22924.8 -> Alright, so we are going to write to this file using

22928.4 -> what using file output Stream So it showing up this

22932.7 -> so I select Java dot IO dot fight.

22935.238 -> All right.

22936.365 -> Okay now I create file output stream.

22944.3 -> Create an instance of it right similar to

22946.814 -> how we did for other programs.

22948.7 -> Now, it says file not found exception has to be handled.

22952.1 -> I choose not to handle it

22954 -> and I throw it back to the calling program.

22956.6 -> All right.

22957.4 -> So now what I do is I do file dot right file output stream.

22964.903 -> I am going to write it to this file.

22971.6 -> So I just write a text here.

22975.4 -> All right.

22976.7 -> So write a text here.

22978.1 -> Hello folks.

22978.7 -> Hope you're enjoying the session and I just closed it off again

22984.9 -> it throws ioexception when you close it.

22987.5 -> So remember we said there could be multiple exceptions

22990.7 -> that could be thrown out of a method.

22992.6 -> So I again I choose to throw this one as well.

22996.5 -> So basically what I'm trying to do here is I throw

22999.9 -> IO exception as well.

23003.1 -> Okay, so it doesn't take a string as a as an input.

23007.1 -> So what I have to do is I have to do not get bites.

23011.3 -> As we saw the Constructor of it constructed

23014.4 -> isn't takes string as input

23016.9 -> in case of output stream or in case of file output stream.

23021.6 -> It interacts in terms

23023 -> of byte array and stuff like that.

23025.2 -> So I converted this string into byte array.

23028.43 -> So when you see get bites get bites method is a method

23032.507 -> on a string class

23033.819 -> which converts the string into array of bytes.

23037.4 -> All right.

23038.093 -> So now what I do is I give a call to this particular.

23049.9 -> I'm writing to a file

23051.405 -> and I'm going to take create a new file.

23055.9 -> So I can take the same file, right?

23057.9 -> I am going to take a b or else I will create a new one.

23064.6 -> All right, so I create a file which is like message dot txt

23069.2 -> or you need not even create it.

23071.103 -> It will create by its own.

23072.7 -> I will delete it may be okay

23074.7 -> on the thing is I love to create see a Eureka yo.

23080.2 -> All right.

23081 -> And here we say message dot txt.

23085.5 -> All right, so I call a method to write to the file using

23090.124 -> file output stream night choose to throw it off

23093.663 -> from here as well.

23095.9 -> Alright, so we have a method

23097.766 -> which is going to write into a file using file output stream.

23101.766 -> All right, so I run this program.

23106.8 -> Okay, it ran successfully.

23108.8 -> Let me open this message and see

23111.1 -> if we have the message written there.

23113.2 -> All right, so you could see here.

23115 -> Hello folks.

23115.646 -> Hope you're enjoying the session

23117.369 -> which is written from your program.

23119.7 -> All right, so this file input stream as well,

23122.288 -> which is pretty much similar it again operates

23125.07 -> in terms of bytes.

23126.039 -> As you could see the signatures of the methods within it

23129.047 -> would read the contents of the file into the byte array

23132 -> that you have passed as a parameter.

23134.1 -> The second one is to read

23135.8 -> from a particular offset the length

23138.1 -> that you have mentioned

23139.452 -> or passed as a parameter close is pretty much similar.

23142.202 -> It would close the connection

23143.79 -> that's been established

23145.1 -> and it would make the class available

23147.4 -> for garbage collector to clean it off.

23150.2 -> Okay garbage collector is nothing but unlike see

23153.4 -> where in you have to delegate the memory location

23156.471 -> that's been used garbage collector is parallel thread

23159.8 -> that is run by jvm to remove the or to free up the memory space

23164.4 -> that's been acquired by classes.

23166.9 -> So it runs sporadically it's not within your control.

23170.062 -> It runs per radically and it clears of the memory locations.

23173.7 -> We have a reed method which is nothing

23176.046 -> but reads the next bite from the input source.

23178.9 -> So on the file input stream instance on which you read it,

23182.619 -> it would read out the next bite and if it's end of the stream,

23186.6 -> it would return -1.

23187.898 -> So the return value is integer

23190 -> as you could see here you could skip specified number

23193.7 -> of bytes from the input stream

23196.7 -> and available Returns the number of bytes

23199.2 -> that can be read from the currents tree,

23202 -> right?

23202.5 -> So maximum number of bytes that could be read out.

23205.4 -> So I'm just going to read through this light

23208.41 -> or if you want.

23209.46 -> Yeah, I can take an example maybe

23211.8 -> since we didn't take example on reader.

23214.5 -> I'll take one example and reader as well.

23217.3 -> Okay, so here I to file input stream demo All right,

23225 -> so we create a class here

23228.4 -> and I have a main method here.

23231.8 -> Okay.

23232.43 -> I have a private method

23234.2 -> which is void and it's not returning anything

23238.1 -> and I said read from file.

23240.7 -> All right.

23242.7 -> which takes file Again, I'll have to import file.

23250.6 -> Okay, so Java dot you could see

23252.9 -> the input statement coming up here.

23255.18 -> So now I create file input stream.

23260.5 -> Okay.

23262.8 -> I create a new instance of it.

23265.7 -> Which would typically take

23267.557 -> for that matter it would take string as well.

23271.8 -> Just to show you a different variant of it.

23274.551 -> It's not that you have to always pass file it you

23277.696 -> could pass string as well.

23279.8 -> Alright, so we are passing a string here.

23282.4 -> It says file not found exception has to be handled

23286.2 -> since its read you have to ensure

23288.6 -> that you have the file there.

23290.2 -> Right?

23291 -> So I choose to again throw off this exception.

23294.6 -> So I'm not handling it.

23296.6 -> So typically you would handle exception

23298.8 -> when you want to do something on it.

23300.8 -> Right when file not found

23302.449 -> if you're trying to read a file and that file doesn't exist

23306.285 -> in your drive.

23307.131 -> I wouldn't handle it.

23308.412 -> I would just throw it off.

23310 -> I want program to break right there.

23312.219 -> Right?

23312.6 -> I don't want it to proceed

23314.149 -> because our program

23315.28 -> at this particular method is trying to read from a file

23318.626 -> and if it doesn't exist it,

23320.3 -> it doesn't make sense to proceed further.

23323.094 -> All right, so I have input stream.

23325.4 -> Now what I do is not read and

23327.861 -> as you could see it's written in integer, right

23331.4 -> so This has to be looped.

23335.7 -> All right.

23336.4 -> This has to be looped until you get minus 1 right.

23340.3 -> So basically you would have like say teacher and you have like

23348.8 -> so this is integer read from file.

23351.4 -> All right, and I keep this as integer,

23354.7 -> which is so whatever you read I need to assign this because I

23360.223 -> want to write that as well.

23362.3 -> All right, so I'm assigning

23364.2 -> to this and unless this is minus 1 you are going

23369.1 -> to read through write it again shows exception,

23372.9 -> which I need to handle.

23374.6 -> So this time it's ioexception

23376.817 -> and I'm going to throw this one as well.

23380 -> All right, so you have a reed method you are going to read it

23383.247 -> and basically till the time its minus 1 it's going

23385.9 -> to be red right now.

23387.222 -> What I'm going to do is within the loop.

23389.8 -> I'm going to just type.

23393.657 -> So basically I'm going to just type cuz this to character.

23399.6 -> It's read as integer.

23401.2 -> So you have to convert it into character.

23403 -> If you want to see in terms of character.

23405 -> If or else you would get the ASCII value of it.

23408.661 -> Alright, once this is done.

23411.3 -> Basically I need to close off the stream as well.

23415.5 -> Okay.

23415.833 -> Now what I do is I create the instance

23418.3 -> of file output stream demo.

23422.3 -> Just nothing, but creating instance of it.

23425 -> Right demo dot read from file.

23428.069 -> But remember this time we are not creating a file instance.

23432.6 -> We are just passing the string.

23434.491 -> All right, so you could take any of this file

23437.261 -> since we are reading it we could take like let me take bike in

23441.1 -> for it just got valued Ducati.

23443.7 -> So I'm passing this as a string this time.

23446.3 -> All right, and it's a different variant.

23448.5 -> You could pass it as a file as well.

23450.347 -> You could pass it as a string as well.

23452.4 -> But since I have been passing as a file in previous examples

23456.5 -> this time I choose to pass it as a string.

23459.7 -> Alright, so now I am throwing it off

23461.9 -> from here as well since I don't want to handle it right.

23465.2 -> So if I get an error, I want the program to break.

23467.9 -> So that's the reason I am throwing it off

23469.9 -> from here as well.

23473.7 -> So coordinator, let's see.

23475.7 -> What's it?

23476.664 -> Okay, so I have to put double slash here.

23479.826 -> All right.

23480.769 -> I miss that one.

23484.5 -> So basically if you don't put double slash it

23487.1 -> would take it as a regular expression sort of again.

23490.1 -> It's not bike in Foods dot txt,

23492.851 -> which I missed I believe

23494.8 -> so it says that bike info file doesn't exist.

23499.3 -> Right since it's a text file, right?

23501.326 -> You have to provide the extension as well.

23506.4 -> All right, so you could see it read in terms

23508.9 -> of characters, right?

23510.3 -> So you could see the first character read as D then then

23514.16 -> you could see it followed till till it red Ducati.

23518.1 -> All right, so that's about file stream

23520.9 -> or file input stream.

23522.4 -> That's how you write programs.

23525.1 -> Now what serialization

23526.2 -> and deserialization I will quickly cover on this one

23529.2 -> since this is something

23530.5 -> that's been used widely in big data when it comes

23533.6 -> to Big Data or when it comes to distributed computing.

23537.2 -> Just not to if you understand it's good.

23539.288 -> If you don't understand you don't have to think much

23542.1 -> but I'm just talking in terms of distributed computing.

23545.247 -> Right?

23545.616 -> So when it comes to Big Data,

23547.4 -> it's not that you have server farms and everything.

23550.8 -> Your program doesn't run on server Farm anymore.

23553.7 -> It's more about you have commodity Hardware

23556.9 -> on which a program is run

23558.7 -> and that's what Big Data Frameworks are good

23561.6 -> about the investments in terms of infrastructure

23565.3 -> by having server Farms has been reduced a lot

23568.7 -> has been cut down a lot

23570.4 -> and you could have commodity Hardware

23572.6 -> on which you could have this distributed Frameworks running.

23576.081 -> So say for example,

23577.2 -> you might have heard about Hadoop or Apache spark,

23580.4 -> which could actually run on normal Hardware right

23584.2 -> or you could Need to on cloud as well.

23586.413 -> So you have like Amazon web service

23588.633 -> which is cloud like you you have Google as well

23591.5 -> Google services,

23592.6 -> which exposes as a cloud you have a seizure,

23595.5 -> which is nothing but Microsoft's Cloud.

23598.06 -> So all these are kind of not big Hardware not server Farms

23601.9 -> that you have.

23602.693 -> It's a normal Hardware that you could configure

23605.3 -> and you could run through your chunks of data

23608.1 -> or petabytes of data

23609.404 -> that comes in from cloud or from elsewhere, right?

23612.6 -> So that's the beauty of it.

23614.339 -> That's the beauty of java and one

23616.356 -> of the main things are main feature

23618.5 -> that Java has got a serialization

23620.755 -> and deserialization

23622.094 -> which helps in having this distributed framework going.

23626 -> Okay.

23626.6 -> So serialization is nothing but you have class

23630 -> right and you you create instance of a class,

23633.257 -> which is nothing but object right now

23635.803 -> this instance of a class

23637.5 -> if you want to pass it over to some other computer

23640.382 -> or some other computer on your network,

23642.4 -> right?

23642.9 -> This could be done just

23644.178 -> because this Serialization there's a concept

23646.6 -> of serialization right suppose.

23648.5 -> I create some object of a class today on my computer.

23652.5 -> And if I want to pass the same state,

23655.2 -> right it's about passing the street

23657.38 -> not the behavior behavior is of course just methods, right?

23661.1 -> So it's about passing the state of the object.

23663.8 -> So whatever state my object is

23665.843 -> or whatever properties my object bolts

23668.243 -> at some particular point

23669.8 -> if I want to pass it over to some other computer

23672.564 -> on the network.

23673.463 -> This could be done just

23674.816 -> because you have serialization was

23676.83 -> what you would do is basically

23678.661 -> if you remember the object stays in Heap right Heap memory,

23682.075 -> which is protected

23683.177 -> which no other process can get into that particular.

23686.3 -> He process Heap memory, right?

23688.656 -> That's a security that Java provides

23691.6 -> if you remember in the first slide we covered it, right.

23694.8 -> So what Java does

23696.061 -> by serialization is whatever contains of a particular object

23700.6 -> or whatever contains a particular object whole

23703.4 -> set any could be written.

23705 -> To your disk as a binary file

23707.469 -> and you could send it over to some other computer via wire,

23712 -> or you could take it plug in your USB drive

23715.4 -> and you could just take that particular file the binary file

23719.1 -> that's created and you can go elsewhere

23722.03 -> and just play that file

23723.8 -> or just deserialize it to see the contents of it.

23727.492 -> Right?

23727.845 -> So you could imagine this is something

23730.021 -> that is needed in terms of distributed computing

23732.705 -> since not everything is been carried out

23735 -> on a single computer you you would process something

23738.108 -> on your computer you would you would write it to a file

23741.4 -> and you need to pass on this file toward

23744.1 -> or transport this file

23745.585 -> to different computer right or typical example in which you

23749.6 -> would think of serialization is more about you.

23752.754 -> Could you could have say

23754.4 -> for example one operation carried out on one computer

23758.262 -> and same operation

23759.6 -> or different operation on a same file carried out

23762.423 -> on some other computer now you

23764.103 -> want to move Just them together and that's

23766.307 -> where you would have serialization

23768.052 -> and deserialization coming into picture basically to understand

23771.7 -> the concept serialization

23773.164 -> is nothing but writing the state of the object to a file

23776.4 -> and deserialization is nothing

23778.4 -> but again taking the state of the object

23781.4 -> that's been written to the file again putting it back

23784.2 -> to a class format

23785.379 -> or when you want to use this serialized class.

23788.5 -> You would basically deserialize it use it.

23791.1 -> So serialization is a process of converting an object mrs.

23794.6 -> To sequence of bytes,

23795.9 -> which can be persisted to a disk or file

23798.9 -> and can be sent through streams or can send across wire

23803.6 -> or could be you could actually take it on your drive

23807 -> and transport it elsewhere the reverse process

23810.1 -> which will convert data bytes into object

23812.1 -> is called D serialization.

23814.3 -> All right.

23815.2 -> So how do we have this serialization

23817.572 -> and deserialization done

23819.18 -> or what classes we have for supporting it.

23821.9 -> Let's talk about that.

23823.321 -> All right in this example.

23825 -> You have a student info

23826.735 -> which is having ID and name, right?

23829.3 -> And basically you could see

23830.978 -> that we have created an instance of student info

23833.9 -> which which has value of 9 and John.

23836.7 -> All right.

23837.319 -> And now what we are doing is we are writing the state state is

23841.173 -> nothing but the value

23842.535 -> that this particular object holds right

23845 -> which is nothing but ID of 9 and name value

23848.5 -> of John, right?

23850 -> So we are writing this into a do a file

23853.3 -> which is nothing but student Dot txt.

23856.7 -> And and we are just writing that to a particular file.

23859.999 -> Okay, and this is nothing but the student dot txt file

23863.3 -> that you see it should be txt.

23864.8 -> Actually.

23865.31 -> It's it's a binary file.

23866.647 -> So you should I would rather prefer to have student dot Pi

23870.2 -> n or binary and you would write it to that file

23873.243 -> using right object.

23874.5 -> So the supporting class

23876.3 -> for serialization is object output stream

23879.237 -> and object input stream.

23881 -> All right, so I will quickly take a demo of this.

23887.3 -> So the first thing that we do is serialization serialization

23890.8 -> is done by object output stream.

23895.1 -> All right.

23895.9 -> So again, we have a main method suppose.

23900.1 -> I want to serialize it.

23902 -> So I would do something like say

23904.5 -> I have a private method which is void,

23907.1 -> which is serialize.

23909.8 -> Okay.

23910.2 -> So the first thing I would want to create

23912.7 -> is nothing but Java class which will hold the state right.

23917 -> So this is a class

23918.058 -> which you want to serialize or which you want to send it

23921.2 -> across two different computers.

23923.1 -> So such losses are known as model classes, right?

23926.196 -> Basically such classes are nothing but classes

23929.073 -> which holds chunks of data.

23930.808 -> So for Simplicity,

23931.904 -> we have taken small data like ID and name,

23935.007 -> but in general you would have like chunks of data.

23938 -> They're all right.

23939.4 -> So here I say Vehicle info.

23943.5 -> Maybe this is the class that I have here.

23946.2 -> Alright, and now

23947.43 -> what I do is suppose I have Suppose I have

23954.853 -> two parameters here.

23958.7 -> All right, so I have two parameters here,

23960.9 -> which is nothing but integer

23963.2 -> and suppose I have like string name of equal.

23970.2 -> Alright, so now I Define a Constructor for vehicle info

23974.3 -> which takes T three parameters for Simplicity number of Wheels.

23979.7 -> First.

23980.2 -> Say for example, I take name of vehicle.

23984 -> then it's number of wheels and say I have one more parameter,

23988.2 -> which is mileage.

23991.1 -> All right.

23992.6 -> Remember we use of this keyword

23995.8 -> since the name of the arguments

23997.713 -> and the name of the instance variables are the same

24000.8 -> we need to use this this DOT number of Wheels.

24006.6 -> Is equal to number of Wheels?

24008.9 -> All right, and this dot mileage is equal to mileage.

24013.8 -> All right.

24014.409 -> So this is a simple model class

24016.325 -> which is supposed to hold values.

24018.207 -> Basically in reality.

24019.419 -> This would be holding like chunks of values.

24021.9 -> Okay.

24022.28 -> Imagine like could be like megabytes

24024.862 -> of information or even huge gigabytes of information.

24028.7 -> All right, but for Simplicity here,

24030.95 -> we are taking this simple class right.

24033.4 -> Now.

24033.6 -> What we want to do is we want to see realize this into a GFI.

24037.342 -> We are going to create an instance

24039.283 -> of this particular class

24040.7 -> and we are going to dry this state

24043.057 -> or whatever values we have that particular instance.

24046.9 -> We are going to write it to a file

24048.897 -> so that it could be read from somewhere else

24051.5 -> or it could be used by any computers on the network.

24055.03 -> All right, so I have vehicle info.

24060.3 -> Again suppose I write BMW is equal to new vehicle info.

24065.1 -> Now, what I have to pass is name of the vehicle,

24068.2 -> which is BMW right number

24070.7 -> of and I pass some value like Like 10, all right.

24077.9 -> Okay.

24078.224 -> Now we have created instance of vehicle info

24080.753 -> and we have passed the values

24082.459 -> that we want to pass it and now we want to see realized this.

24086 -> Okay.

24086.349 -> So how do we see realize is nothing but we use

24089.5 -> object output stream, right?

24096.8 -> So what does it take?

24100.3 -> So basically you could go into the source code and

24103.414 -> if you want to deal more you could actually

24106.205 -> see what other Constructors

24108 -> that it takes.

24110.1 -> You could see it takes output stream.

24114.302 -> So one is output stream as a Constructor.

24120.2 -> If it takes output stream,

24122.2 -> then I'll have to create file or stream.

24125.8 -> Basically.

24126.3 -> I will name this as

24127.8 -> object stream and this one would be filestream.

24132.6 -> Okay, I create a new file output stream

24136.4 -> and you could pass the file on which you want to write it.

24139.972 -> All right.

24140.599 -> So in this case the file

24142.14 -> on which I want to write a particular class.

24144.9 -> I will pass it as file

24146.529 -> and I'll be passing it over here.

24148.9 -> All right.

24149.7 -> So what I am trying to do here is resolve this okay.

24153.6 -> So you take the file or to which you want to see realize

24157.4 -> so basically this vehicle info would be serialized

24160.511 -> into this file

24161.4 -> and this file would be transported anywhere

24163.5 -> across your network.

24164.8 -> So it shows file not found exception again,

24167.999 -> I choose to throw it.

24169.8 -> It shows my exception now,

24173.12 -> I've passed this file stream here.

24176.3 -> Alright, so this is how we usually write programs.

24179.9 -> You have file input stream file output stream,

24183.2 -> which is nothing but the file

24184.995 -> to which you want to write write the state of the object

24188.4 -> and you instantiate object output stream.

24191.8 -> Okay.

24192.4 -> Now let me write to it.

24195.7 -> Okay.

24196.8 -> So basically what are you going to write is nothing

24199.8 -> but vehicle info just instance of okay.

24204.6 -> So you're going to you want to write this instance

24207.1 -> of vehicle info particular instance of vehicle info

24210.7 -> into your into the file?

24212.546 -> Okay.

24213.1 -> So I write something like this.

24216.4 -> Okay.

24216.8 -> So so basically

24219.015 -> what we'll have to do here is whenever you have this thing

24223.531 -> whenever you want to write

24225.5 -> or whenever you want to write the state

24228.1 -> of a class to a file you need to implement one interface,

24233.202 -> which is serializable.

24235 -> All right.

24235.646 -> It's a do-nothing interface.

24237.8 -> It's just used by it's a mock-up interface as

24240.7 -> well marker interface rather.

24242.65 -> It is just used by jvm to say

24244.6 -> that this particular class could be serialized

24247.194 -> but it doesn't have any methods within it

24249.5 -> as you could see if it would.

24251.5 -> I've had some methods it would have shown an error saying

24254.3 -> that you should implement it.

24255.935 -> But in this case it didn't because it doesn't have

24258.7 -> any methods within right?

24262.4 -> So basically when you have object streamed, right?

24267 -> Okay, so it takes all right.

24270.3 -> So we we create objects stream

24272.7 -> and we pass the file that we want to write to

24276 -> and we have right object method which would take the instance

24279.869 -> of the class that you want to write and we have

24282.836 -> like we flush it and we close it.

24284.9 -> So one thing to note here is vehicle info class has

24288.9 -> to implement serializable.

24290.9 -> That's a marker interface serializable is nothing

24294.023 -> but a marker interface

24295.443 -> and it doesn't have any method within it is just an indicator

24299.292 -> as you could see it's an empty interface.

24301.858 -> All right.

24302.5 -> This is the source code of it.

24304 -> You could see it's an empty interface.

24306.2 -> It is just a marker

24307.5 -> or it is just a notification to the jvm saying

24310.9 -> that this class is something that could be serialized.

24314.6 -> Alright, so we have this class

24317.5 -> and we are going to serialize the state

24320.5 -> of BMW object into a Phi.

24323.6 -> Alright, so now

24324.753 -> what I do is I create Object output stream demo

24330.2 -> and I call serialized

24332 -> within it now this serializes taking two parameters.

24336.5 -> So if the first parameter is this is other way of passing it.

24341.3 -> We are not actually creating instance.

24343.5 -> We are passing it directly.

24345.3 -> All right, so I pass this and I say serialized file.

24352.5 -> Okay, maybe dot bin and the other parameter

24356.6 -> that it's taking is nothing but the instance of class

24360.5 -> that you want to serialize.

24362.4 -> Alright, so here we are again getting exception

24365.7 -> which needs to be thrown off.

24368.5 -> Alright, so this is a simple class that we

24370.7 -> have we have vehicle info

24372.6 -> which carries BMW instance

24375 -> or we have created instance of vehicle info with BMW values

24379.4 -> and we are trying to serialize this to the to a file

24383.148 -> which is serialized file dot bin.

24385.6 -> Okay.

24386.435 -> Let me see if it runs.

24391.6 -> Alright, so I hope it ran now.

24394.3 -> This is a binary file.

24395.4 -> If you see you are not going to understand everything

24398.156 -> that you have within this file.

24399.8 -> Okay, so I

24401.9 -> just Okay, so here you could see it's not something that could be

24410.7 -> completely readable,

24411.987 -> but you could get some idea about it.

24414.3 -> It's during game W.

24415.6 -> All right, and this is not meant

24417.3 -> for you to read it writes not in a human readable form.

24420.826 -> This is basically for passing this over a network

24424.012 -> and at the other end you would deserialize it.

24426.973 -> Alright, so this is how we see realized it now.

24430 -> We will check on how we deserialize it.

24432.345 -> All right.

24432.986 -> So you you saw the contents right?

24435.1 -> It's something that is not readable.

24437.6 -> Okay again, I'll open it up.

24442 -> Not everything would make sense.

24443.6 -> But you could see that this is for BMW.

24447.7 -> So basically you could see the value BMW here, right?

24451.8 -> So now what I do is I want to see see realize this right.

24456.3 -> So this is how you see realize it.

24458.6 -> We spoke about it

24459.7 -> how we see realized it now we are going to deserialize this.

24463.4 -> So basically this deserialization won't happen

24466.263 -> on the same computer.

24467.596 -> It might or might not or it could be saved

24470.4 -> different application within the same computer as well.

24473.217 -> So if you have two applications running

24475.22 -> and want to interact between the two applications

24477.9 -> running on the same computer could use serialization

24481.2 -> and deserialization or you could majority of the use case

24484.718 -> for this feature is more

24486.145 -> about passing it over the network.

24488.241 -> All right.

24488.893 -> So, let's see how we deserialize it.

24491.3 -> Okay.

24491.672 -> So when you easy realize it you use object input stream.

24495.789 -> Okay, so in the same class or I'll just for Simplicity sake

24501.15 -> I'll change this to object stream demo

24503.997 -> because this is not just all right,

24509.9 -> so I Defector it

24511.396 -> and I change we name this too.

24515.5 -> Okay, so this is been renamed to object stream demo now

24519.6 -> create a private method,

24521.3 -> which is nothing but void deserialize.

24525.5 -> Again First DC realization you need to have the file right

24529.6 -> you could imagine of you having the file and file

24533.8 -> should be okay.

24536.8 -> Okay.

24537.2 -> So now what we do is

24540.8 -> basically we could have this as a file rather

24545.4 -> since we are going to send the same file.

24550.061 -> Same file for DC realizing as well.

24552.676 -> So it's better to have it defined here.

24555.6 -> And you pass it as CD list.

24558.5 -> Okay so far we have serialized

24560.6 -> it now we are going to deserialize it.

24562.77 -> So what you do in D serialization is nothing

24565.5 -> but you use object.

24567.8 -> So the first thing

24568.874 -> that you will have to create similar to be created

24571.8 -> file input stream about now,

24573.611 -> we are going to file output stream in the serialized case,

24577.3 -> but here we are going to create a file input stream.

24582.2 -> And a provide the fight here.

24584.421 -> Alright, so we have file input stream created now

24588.1 -> we have object input stream.

24594.1 -> Alright, we are creating instance of it and it

24597.372 -> would be new object input stream

24599.7 -> and you would be passing the fill input stream

24602.593 -> that you created the step

24604.2 -> above all red showing you for exception.

24607.1 -> You have to could either throw it or you could handle it.

24611.6 -> So this case I'm throwing it off.

24614 -> Alright, so we have

24616.53 -> so here you could see we had bright object now,

24620.3 -> I'll have read object.

24622.2 -> So read object throws filenotfoundexception or class

24626.3 -> not found exception

24627.502 -> that you need to handle right again through it.

24630.871 -> So here you could see IO exception

24633.053 -> and class not found exception right single method

24636.227 -> can choose to throw multiple exceptions from within.

24639.7 -> All right, so we have chosen to throw it now we

24643.5 -> have vehicle info or we don't know

24648 -> whether it's BMW at that point.

24650.384 -> So I say d serialized object.

24656.1 -> All right, so object streamed read object by default.

24660.2 -> It returns object type.

24662.3 -> So we need to we need to type casted.

24665.4 -> This is how we typecasted one form to the other.

24668.464 -> So basically we know that object streamed

24671 -> or read object is going to give us vehicle info object.

24674.832 -> That's why we can actually type cast it.

24677.6 -> All right.

24678.287 -> So now what I do is

24679.593 -> once I get this D serialized object,

24682 -> I'm going to print out the values that I have within.

24685 -> All right, so I'm going to print the name of the vehicle.

24688.5 -> So I say All right put us.

24700.4 -> Right, so name of the vehicle the serialized file similarly.

24705.038 -> I just copy paste.

24706.423 -> It will print number of Wheels Alright

24713.4 -> and we'll print mileage of we go I need this one.

24718.5 -> Alright, so basically we are serializing it

24720.999 -> and then DC realizing it after deer is realizing it.

24724.1 -> We are printing the value of the contents

24726.3 -> or we are printing the contents of a particular object to see

24730 -> if it is what we expect.

24732 -> All right, so maybe I can do one thing.

24734.596 -> I can delete this off.

24736.2 -> Let me close this and let me delete this off.

24740 -> Okay.

24740.352 -> I'm deleting serialized info.

24742.4 -> I'm going to run this program again

24744.2 -> and this program will serialize and deserialize it.

24747.9 -> Okay, it will see realize it in the first case.

24750.8 -> And now I'm going to write would be serialization deserialized

24754.675 -> and the serialized file.

24756.211 -> All right now here as well.

24758.3 -> I am going to throw away.

24760.7 -> Okay.

24761.5 -> So first we are going to serialize it

24763.6 -> and then we are going to deserialize it and see

24766.5 -> whether we get the contents that we expect.

24769.4 -> All right, so it's running.

24771.3 -> Let's see if the file has been created.

24773.6 -> So we deleted the files.

24775.085 -> It's not yet come.

24777.1 -> So we can see that a file was created here.

24780.011 -> Right which is a serialized file and we printed the value

24784.391 -> from be serialized file as well after DC realization.

24787.9 -> We printed the value of the contents

24790 -> in the serialized file just

24792 -> like we got the expected value which was BMW 4 and 10,

24796.738 -> which you had said.

24798.2 -> So basically what we are doing here is we

24800.2 -> are storing the state of a class

24802.1 -> or state of the object

24803.502 -> to a disk and this could be transported anywhere

24806.5 -> when I say it could be transported is nothing but

24809.323 -> this is just a binary file,

24810.823 -> right so you could take it into your text file

24813.47 -> or you could take it into your pen drive

24815.775 -> and you could take it anywhere.

24817.6 -> All right.

24818.199 -> So that's the beauty of serialization

24820.015 -> and deserialization.

24821.029 -> I spent more time on this

24822.335 -> because this is something that is very important

24825.1 -> for Big Data

24825.9 -> since big data is nothing but all the big data Frameworks

24829.194 -> that we have they follow distributed computing

24831.918 -> and this is one of the important internals

24834.4 -> of distributed computing

24836 -> though you need not.

24837.111 -> Take care of it.

24837.991 -> It's all taken care by the Big Data framework.

24840.394 -> But this is an important concept to understand.

24843.1 -> All right, so let me quickly talk about wrapper classes.

24846.766 -> It's not an important topic

24848.5 -> to but I will quickly cover on this thing.

24851.1 -> So wrapper classes are nothing but you have

24853.283 -> primitive data types

24854.269 -> that we discussed the first day, right?

24856.26 -> So initially we didn't have this wrapper classes in picture

24859.3 -> when the initial version of java was created.

24861.9 -> So data types were dealt

24863.67 -> in terms of primitive data type itself.

24866.4 -> Then since Java is object oriented, right?

24869.3 -> It has to be completely object-oriented so they

24872.2 -> came up with a concept

24873.3 -> that we shouldn't be dealing data types as

24876.1 -> a primitive data type rather.

24877.989 -> We should be having some sort of object to it

24880.8 -> which is rapper,

24881.825 -> right which is wrapping this primitive data type.

24884.9 -> So in order to make it completely object-oriented

24888.3 -> they have come up with this wrapper classes,

24890.6 -> right so int when you define int right

24893.6 -> if you define int something of this sort,

24896.621 -> it's Native whereas you would have something like this.

24901.6 -> Inti is going to be primitive data type

24904.7 -> and whereas you would have something like this

24907.472 -> which is nothing but wrapper class, right?

24910 -> So if you go into the wrapper class,

24911.75 -> you could go into the source code and see it's nothing

24914.4 -> but it's doing the same thing.

24915.9 -> It has got some utility methods as well on the top of it,

24919.002 -> but basically it storing your value.

24922.4 -> So for now they have changed the source code quite a bit.

24925.6 -> Basically, it's touring in terms of characters, I believe.

24928.9 -> All right, so you need not take care of this.

24931.099 -> But what I am trying to say is wrapper class is nothing

24933.8 -> but a rapper built upon the primitive data type

24937 -> so that everything is taken care in terms of classes since it's

24941.368 -> completely object-oriented programming language, right?

24945.077 -> So Java has a class dedicated to each of the Primitive types.

24949.2 -> These are known as wrapper classes

24950.9 -> because they wrap the primitive data type

24952.9 -> into the object of that class.

24954.5 -> All right, so you could see for bite you have a wrapper class

24957.8 -> corresponding wrapper class as bite with starts with capital.

24961.5 -> Be all right,

24962.7 -> since it's a class it has to start with uppercase

24965.8 -> or it has to follow camel casing short

24968.8 -> has again short int has integer long has long float.

24973.9 -> You could see a corresponding wrapper class

24977.1 -> with name float double

24978.9 -> will have double character CH AR will have character

24983 -> which starts with a bouquet see again Boolean again has

24987.021 -> camel cased Boolean as its wrapper class.

24990.1 -> All right, so

24990.927 -> when it comes to classes you could have hierarchy.

24994.176 -> So basically you could see

24995.9 -> that all this byte short integer long float double.

25000.33 -> Everything is subclassed from number.

25003.1 -> So basically in the source code

25004.9 -> that we saw for integer you could see

25007.437 -> it's extending number right?

25009.1 -> So that's what it is saying here is a subclass

25011.7 -> of number integer is a subclass of number.

25015.2 -> So how do we reduce wrapper class?

25017.8 -> It's basically you just have to pass value to it.

25021.3 -> You could have as a part of Constructor,

25023.8 -> you could pass some kind of value to it.

25026.8 -> So you could either assign value of hundred right

25030.492 -> or you could have something like Something like this.

25036.6 -> Okay.

25036.8 -> So you have different variants of it.

25038.6 -> You could either create it directly assign

25040.898 -> literal value to it,

25042.099 -> or you could have something like this but

25044.752 -> as you could see this is deprecated.

25046.811 -> This is no longer required.

25048.4 -> Actually.

25049 -> It is still accepting it.

25050.512 -> It's not throwing compile time error,

25052.659 -> but it's deprecated.

25053.836 -> Which means if you're writing a new code,

25056.2 -> you shouldn't be writing it this way.

25059.1 -> So there's also concept of Auto boxing

25061.696 -> which is nothing but

25063.1 -> if you have like integer a could be assigned value K directly.

25068.6 -> All right, or could be assigned value J directly.

25071.9 -> So it could be converted from wrapper class

25074.9 -> into your primitive type without any kind of conversion.

25078.7 -> That is known as Auto boxing.

25080.846 -> It does it by itself?

25082.4 -> What is generic in Java generic is nothing but template in C C++

25087.3 -> in C++ rather you have you define a template

25090.748 -> which is which is a general.

25093 -> Thing you're not putting in

25094.7 -> a specific data type you are saying

25096.4 -> that this is what it is.

25097.6 -> It's a template

25098.64 -> and you could have any data type during runtime.

25101.9 -> So basically what you're trying to say is this particular method

25106.1 -> or this particular class is a generic class,

25109.4 -> which could handle any data type that is passed.

25112.799 -> So it's not specific.

25114.4 -> All right.

25115.392 -> So generics in Java is similar

25117.7 -> to templates in C++ generique enabled type parameters

25122.2 -> when defining classes interfaces and methods, right?

25126.3 -> So the type parameter is nothing

25128.265 -> but a generic type and it's not saying

25130.7 -> that it's going to deal just with integer or with character

25134.4 -> or with string.

25135.445 -> It is saying that it could handle anything

25138.249 -> that comes anytime that you would send it any type

25141.7 -> that you would instant.

25143.265 -> She ate that class with.

25144.9 -> All right.

25145.935 -> So when we take example,

25147.834 -> you should get some more idea about this generate

25151.484 -> provide compile time.

25153.1 -> Type safety allowing programmers

25155.391 -> to catch invalid types at the compile time.

25158.4 -> So generics work on type Erasure,

25161 -> which is nothing but which is done

25162.9 -> at the compile time itself.

25164.5 -> Basically, it's done at the compile time.

25166.563 -> It can catch exhibitions during the compile time itself,

25169.4 -> or it could prompt you during the compile time itself, right?

25173.092 -> We can specify the type the angular brackets.

25175.8 -> So whatever type you want to do,

25177.4 -> whatever type is that class going

25179.8 -> to handle we can put it into angular brackets,

25183.2 -> which makes it generate right?

25185.2 -> So here you could see

25186.554 -> that this is a method which is print array

25189.2 -> which is taking e as type.

25190.92 -> So as you could see he is the type here.

25193.7 -> All right, he is a type here and we are not mentioning

25197.343 -> that it is going to take print integer array

25200.1 -> or string array or something of that sort.

25202.683 -> We are seeing that it generates.

25204.624 -> So whatever you pass

25205.912 -> or whatever you instantiate it with

25208.1 -> it's going to take that array and print elements within it.

25212 -> All right, so this Method could be thought

25214.411 -> of as a generic method,

25215.798 -> right you could think

25217.065 -> of this printer as a generic method not a method

25219.9 -> which is just taking integer and printing it.

25222.1 -> It could be string array or it could be anything else.

25225.5 -> So that's what generic means advantages

25228.184 -> of generics type safety objects

25230.33 -> or single type can be stored in generics.

25233.1 -> We would be looking at it

25234.662 -> in the next example typecasting is not required.

25238.2 -> There is no need to type casters

25239.8 -> because it knows that what kind of objects

25242.3 -> that particular data structure would carry

25244.8 -> or hold compile time checking it checks type mismatch error

25248.5 -> in compile time,

25249.518 -> which avoids runtime errors.

25251.3 -> All right.

25252 -> So imagine a list

25253.7 -> which we are going to talk in further slides what is list,

25257.1 -> but imagine a list which is a collection.

25259.9 -> All right, and you have like imagine a list

25262.982 -> which is holding strings.

25264.866 -> All right, so you have list

25266.907 -> dot add and you you add a direct cut to it.

25270.4 -> Now when you get 0 typically

25272.6 -> get Zero would have object the return type would be object

25277 -> since it doesn't know

25278 -> that it is just carrying string know where you have mentioned

25281.1 -> that it is a string of

25282.662 -> it's a list of string right?

25284.651 -> It's a generic list

25286.006 -> so it could hold integer value as well.

25288.674 -> Alright, so in that case,

25290.361 -> what you need to do is when you do list dot get 0

25293.6 -> you have to Typecast to the string here.

25296.145 -> The next element could be integer.

25298.273 -> We don't know right

25299.5 -> since we haven't said that it's a list of string.

25302.3 -> So that's that the reason you need to have typecasting done.

25305.8 -> All right now using generics you could Define

25308.789 -> that this list is a list of string.

25311.1 -> All right, it's going to carry only string nothing else.

25314.5 -> It's going to hold now.

25316.1 -> It makes it simple right you add either a car now.

25319.142 -> If you try to during the compile time itself,

25321.992 -> if you try to add integer to it,

25324 -> like list dot add hundred.

25325.8 -> It would throw an error saying

25327.3 -> that it cannot pulled integer because it's meant for string.

25330.8 -> So that's the advantage that you get over.

25333.1 -> Rick's you could hold it you could catch errors

25336.266 -> during the compile time itself.

25338.6 -> All right, so it won't allow you to add

25342.2 -> or it won't allow you to put a hundred

25344.746 -> in to your list of string.

25346.573 -> All right, and

25347.538 -> since we know it's going to hold only string there's no need

25351.607 -> of typecasting it as well.

25353.46 -> You can see here.

25354.582 -> It's not typecasting it

25356.1 -> in this case you had to put this string here, right?

25360 -> So basically in this case, you need not type custard.

25363.3 -> There's no type question required

25364.9 -> because we know it's a list of string now

25367.3 -> what a collection Frameworks collections framework is nothing

25371.2 -> but you have data structures in terms of classes.

25375.2 -> Again, it's a wrapper for data structure.

25377.7 -> All right, it's nothing

25379.1 -> but like you have array which is normal primitive arrays,

25383.1 -> but this one would be sort of growing array.

25386.2 -> So basically you need not take care of actually,

25389.5 -> you know adding up indexes to it.

25391.7 -> It would automatically It's a self growable array.

25395.3 -> So you could imagine

25396.7 -> when it comes to array you could imagine collection.

25399.9 -> You could imagine one of the classes

25402.295 -> within collection is list,

25404 -> which is nothing but growable array of any data type.

25407.8 -> All right,

25408.3 -> so Java Collections framework provides an architecture

25411.9 -> to store and manipulate a group of objects

25414.9 -> or Java Collections framework includes the following it

25418.1 -> has interfaces classes

25419.615 -> and algorithm interfaces is nothing but again specification.

25423.678 -> This is how it should be.

25425.371 -> So Java says that you know,

25427.2 -> when you have a list it should have so-and-so methods

25430.4 -> like adding to the list setting

25432.269 -> to the list removing

25433.455 -> some elements to the list something of that sort.

25436.4 -> So it defines collection you have a collection you

25439.708 -> should have so-and-so methods

25441.6 -> and list should have so-and-so methods and so on and so forth.

25445.4 -> So basically it's for specification classes is nothing

25448.682 -> but concrete implementation

25450.354 -> so list by itself would have Would have all the methods

25454.511 -> that you just the it's an interface, right?

25457.123 -> So it would have all the methods

25459.1 -> that you want without any implementation.

25461.705 -> But this classes would be actually

25463.8 -> implementing it or rather.

25465.568 -> It would be implementing this interfaces

25468.222 -> and would be giving a concrete implementation for methods.

25472.2 -> Right?

25472.7 -> So as you could read here,

25474.7 -> it's concrete implementations of collection interfaces

25478.579 -> in essence.

25479.379 -> They are reusable data structures,

25481.7 -> right algorithm is nothing but there are utility algorithms

25484.905 -> that you have like

25485.903 -> if you want to sort a particular collection or

25488.4 -> if you want to sort a list list of string you could do it using

25492.589 -> using your algorithm using a predefined algorithms

25495.9 -> that already comes pre-loaded with Java.

25498.4 -> All right when I say algorithms

25500.525 -> and where are these algorithms residing?

25503.183 -> It is a class which is collections.

25505.5 -> So you have a collection

25507.057 -> which is an interface top level interface

25509.879 -> and you have a collections class which is class.

25513.094 -> Which is holding all the utility methods or algorithms,

25516.596 -> whatever you call

25517.7 -> who basically you could just read through this hierarchy.

25520.77 -> These are different types of data structures

25523.3 -> that has been supported by Java.

25525.4 -> You have a collection.

25526.9 -> So the top level interface is

25528.9 -> as you could see there's collection,

25531.038 -> which is extending I treble all right,

25533.372 -> extending iterable interface collection itself is

25536.5 -> an interface you have a list as interface,

25539.6 -> which is extending collection.

25541.3 -> All right.

25542.1 -> So list is extending collection Q is extending collection set

25546.8 -> is extending collection.

25548.417 -> So we have three distinct type

25550.4 -> of data structures Year's list queue

25552.757 -> and set list is nothing but you could say it's a ordered one,

25556.8 -> right it maintains the insertion order write

25559.9 -> the order in which you inserted data into the list

25563.3 -> Q is nothing but first in first out

25565.849 -> and whatever you push in first would come out first

25569.6 -> and set is nothing but To sit in mathematical form right over

25575.4 -> in you have unique values.

25577.2 -> You cannot have duplicate values.

25578.8 -> So that's what set is but it's it need not be ordered.

25582.5 -> It need not maintain the insertion order, right?

25585.8 -> So you have the concrete implementations for list

25589.4 -> our array list,

25590.6 -> which is nothing but again similar to array

25593.432 -> that we have right the normal primitive array

25596.4 -> that we use.

25597.304 -> So it's a wrapper class for it.

25599.524 -> We have a linked list.

25601.1 -> Alright, so this linked list is nothing but doubly linked list.

25605.259 -> All right, so you could insert from you could Traverse

25608.815 -> the either direction you have Vector as well

25611.7 -> which is which is Legacy Forum,

25613.833 -> which is not used to that extent yet as of now.

25617 -> So we have vector and we have a stack

25619.845 -> which extends this Vector redstack is nothing

25623.4 -> but last in first out

25624.9 -> and it adds some more capability on the top of this Vector,

25628.8 -> which is nothing

25629.808 -> but it's a subclass of Victor.

25631.7 -> All right, so these are Implementations

25634.1 -> of list we have a Q and as you could see here,

25637.638 -> there's one interface here DQ which is nothing

25641.1 -> but it is extending Q. Alright

25643.9 -> and we have an array D Cube which is implementation of TQ.

25648.3 -> All right.

25648.931 -> It's a class which is implementing DQ interface.

25651.9 -> All right, this is a priority queue as well,

25654.3 -> which is a class which is implementing Q

25657.163 -> when it comes to set we have a sorted set

25660.211 -> which is again an interface which is extending set

25663.8 -> and as you could see there is a tree set,

25666.311 -> which is a concrete implementation of sortedset

25669.2 -> and it sorts the element that you put into a set.

25672.4 -> It sorts it into a specific order.

25674.6 -> All right, again,

25675.7 -> the concrete implementation of set f is our hash set

25679.3 -> which is nothing but which does some kind of hashing

25682.46 -> which is a default implementation of set

25684.8 -> and which doesn't maintain insertion order

25687.627 -> as set is nothing

25688.8 -> but it is indexed to for fast reversal

25692.3 -> or Want to go get something out of a set,

25695.174 -> its kind of indexed set.

25696.9 -> You could say right it has buckets and everything.

25700.148 -> It follows hashing algorithm,

25701.936 -> right which is

25702.8 -> which is basically for indexing

25704.6 -> or which is basically meant for retrieving data faster

25707.8 -> from the hash set from the set and that implementation.

25711.3 -> That's the default implementation which is

25713.533 -> has said, all right,

25714.598 -> there is a linked hash set which maintains the insertion order.

25717.864 -> All right.

25718.488 -> This has said doesn't maintain the internet insertion order.

25721.6 -> So if you put X & Y into your hash set

25724.4 -> and if you retrieve it or if you Traverse through it

25727.743 -> and print the values,

25729.166 -> it's not mandatory

25730.327 -> that you would get X and Y in the same order

25733.1 -> whereas in the linked has set its pretty much you could be

25736.956 -> a hundred percent sure that X would come

25739.339 -> before why all right.

25740.541 -> So it maintains insertion order what is less list has

25743.8 -> nothing but an ordered collection of elements

25746.3 -> which can contain

25747.397 -> duplicate son like sect it can contain duplicates,

25750.672 -> but it has ordered an unlike say State has ordered write lists

25754.7 -> are further classified into following arraylist linked list

25758.3 -> and vectors, right?

25759.6 -> So based on the use case,

25761.9 -> you could select one of these data structures.

25764.883 -> Let's talk about array list arraylist is nothing

25768 -> but similar to arrays

25769.4 -> that we had and here you could see element stored

25772.728 -> within of size 5-a released

25774.6 -> of size 5 and you could see value stored within right.

25778.687 -> So this is how you instantiate

25781 -> an arraylist array list object is equal to new arraylist

25784.996 -> and you have an arraylist created one of the main things

25789.142 -> about arraylist is

25790.5 -> as I said itself growable

25792.422 -> or its Dynamic you unlike array the normal primitive array

25796.8 -> where in you had to within your square brackets,

25799.798 -> you had to mention the size of the array

25802.193 -> during the Declaration itself.

25803.9 -> Whereas in Array list,

25805.4 -> you need not have to mention this sighs.

25808.1 -> All right, it grows by itself as then

25810.421 -> when you insert data into it, it would go

25813.1 -> So basically you could imagine a normal

25815.9 -> in general scenarios or in most

25818.2 -> of the programming cases or in most of the real use cases.

25822.8 -> You don't know up front.

25824.459 -> What is the size of data

25826.05 -> that a particular array is going to hold right.

25829.1 -> Now the number of elements that a particular array

25831.708 -> is going to hold you cannot know it up front

25833.981 -> because things are Dynamic right?

25835.663 -> So suppose you are reading from the database.

25837.975 -> You don't know what that size

25839.5 -> of the data or what what are the number of elements

25842 -> that a particular database is going to have.

25844.5 -> So typically you

25846.8 -> could imagine real cases you would go with arraylist

25850.859 -> and not primitive arrays.

25852.9 -> All right.

25853.527 -> So also you could imagine this is this is this is saving

25857.092 -> us in terms of memory

25858.5 -> because we are not hard coding the values of it.

25861.7 -> So by default,

25862.8 -> it starts with 10 size of 10 and then it keeps growing as

25866.6 -> and when you insert it.

25868 -> So again, it has a logic it doesn't keep going for each

25871.4 -> and every That you do

25873.4 -> but it has a logic within to grow it

25876.057 -> by particular size.

25877.598 -> So which is all optimized

25879.521 -> which is good for your for your cases use cases.

25884.7 -> So these are the methods that we have within our A-list.

25887.5 -> It's very straightforward.

25889.1 -> When you do add it appends the specific.

25891.792 -> It's usually add and not collection for collection.

25895.3 -> You have a doll methods.

25896.957 -> So it's a typo here you have ad and

25899.504 -> you you mention an element

25901.3 -> that you want to insert into a list

25903.5 -> if it's a string you would have

25905.695 -> string string element or if it's something else

25908.9 -> if it's an integer,

25910.1 -> you would have integer element you could add it

25912.729 -> to a particular index you

25914.2 -> could clear it removes all the elements

25916.4 -> from the list you could have last index

25918.7 -> of a written the index of this list of the last occurrence

25922.426 -> of the mentioned object.

25923.963 -> So if you have multiple

25925.444 -> as we said they could be duplicate values within but

25928.684 -> when you give last index of it's giving you the last index

25932.871 -> All right last index of the object

25934.912 -> that's been passed you could clone it.

25937.7 -> So it's basically coming clone is nothing but a method

25940.9 -> that they're within your object class

25943.7 -> and it would shallow copy the array list.

25946.3 -> So whatever list you have there would be a clone of it.

25949.7 -> Right so clone is as we could see it's

25952.276 -> it's it's from the object class.

25954.42 -> So any class that you create could be clone.

25957.3 -> All right, then you have to array

25959.287 -> so you could have an array list and

25961.406 -> if you want to convert it into a primitive array and use it

25965.038 -> in some form you could do that thing as well

25967.795 -> by doing two array you could trim to size.

25970.5 -> So trim to size is nothing but prims the capacity

25973.7 -> of this array list instance to the list current size.

25977.3 -> All right.

25977.931 -> So whatever is the size

25979.32 -> it would trim to that so moving on let us understand

25982.4 -> how we can Traverse through a list of collection.

25985.4 -> So travel cell is done through I traitor interface.

25988.945 -> Okay.

25989.3 -> So basically you have a nitrate interface and that's

25992.3 -> how you Traverse it.

25993.7 -> Basically you have implementations of it

25996.057 -> since it's an interface it is it is just

25998.455 -> the specification you would have an implementation of it.

26001.9 -> So I traitor is an interface that I traits the elements.

26006.053 -> It is used to Traverse The Collection access

26009.494 -> the data element

26010.7 -> and remove the data elements of the collection.

26013.187 -> All right, it's used for traversal as well

26015.517 -> as removal of data elements within the collection.

26018.4 -> Okay.

26018.703 -> So what are the methods

26020.1 -> that we have within I traitor first is has next.

26023.2 -> So it's it's nothing

26024.376 -> but as you could imagine it is written in Boolean.

26027.1 -> So if it has a next element it would return you true.

26030.8 -> Okay, and if it doesn't then

26032.8 -> if the arraylist is already exhausted

26035.402 -> then it would give you false.

26037.5 -> So you would I basically

26038.9 -> would have a loop wherein you would see

26041.1 -> if it has a name next right

26043.116 -> and if it has next you could This is the next element

26047.2 -> using next Method

26048.6 -> All right, so next would return the actual object

26052 -> and to remove it you could do I treated or remove

26055.5 -> which removes the last element written by the I traitor.

26059.8 -> Alright, so here you could see

26061.3 -> how I treat her is being used you

26063.56 -> have you declare an array list

26065.676 -> and you you I trade through it

26067.791 -> and you print the elements so quickly we can take this.

26074.2 -> So basically I do calm dot edu Rekha dot I

26080.5 -> create one more package now for arraylist.

26083.4 -> Okay, Isaac collections, demo dot array list.

26092.5 -> All right, so I have this particular class created now.

26096 -> I create a main method and I create private void.

26105.2 -> I write a method

26106.5 -> which is create array list for demo.

26110 -> All right,

26110.769 -> as you could imagine when I see create it's going

26113.8 -> to return an arraylist.

26116.4 -> All right, we want it to return list.

26119.8 -> Okay, what I do here is I would create list

26124.1 -> and this list is going to be list of string.

26127.9 -> Okay, imagine generic

26129.5 -> that we spoke about you are saying

26131.5 -> that it is going to be list of string now,

26133.8 -> it's three mirrors saying which list I want it's going

26137.186 -> to be Java dot util

26138.4 -> so you could see Java dot util doll wrist here.

26141.5 -> Now.

26142.2 -> I say it's strings dot new.

26145.661 -> I didn't list.

26149 -> You're saying that here

26150.642 -> what we are doing is we are instantiated.

26153.9 -> So we have a list of strings and we are instantiated it

26157.602 -> since we want arraylist.

26159.277 -> It's going to be a release.

26161.161 -> So here you could see array list being imported as well.

26165.3 -> All right.

26165.8 -> Now what we are going to do here is we are going

26168.2 -> to add some values to it strings dot add

26171.8 -> or maybe I will put again

26174.9 -> since we have been talking about cars

26177.6 -> and bikes I will cars right?

26179.961 -> So we are creating here cars list of car.

26183.1 -> All right, so I put BMW But what?

26193.2 -> all right, so all German cars and then we Then we written it.

26199.8 -> We are returning this.

26200.9 -> So we are creating a collection.

26202.3 -> Right and we are inserting data into it

26205 -> and we are returning it.

26206.2 -> All right, so this would create a list for me right now.

26209.6 -> I want to I trade this list, okay.

26213.788 -> So I create a private method which would return void

26217.8 -> and which food print arraylist or demo.

26224.3 -> All right.

26225.043 -> So as you could imagine

26226.788 -> this is going to take a list as parameter.

26229.9 -> All right list list to be printed

26233 -> or it's pretty much implicit

26235.8 -> or implied that list is whatever list you pass

26239 -> as a parameter is going to be taken for printing.

26242.199 -> Okay.

26243 -> So here what I would do is list dot I traitor

26247.3 -> I take the I traitor.

26249 -> Okay, so I get the list I traitor

26252.2 -> I say I traitor and it's a list

26256.6 -> I traitor All right.

26258.7 -> So I take this list I traitor

26260.9 -> and I say list right

26262.9 -> while while it has any elements within so,

26266.9 -> how do we check with

26268.017 -> whether it has elements within is nothing but dot

26270.7 -> has next if you remember

26272.2 -> while it has any elements within what we are going

26275.3 -> to do is we are going to print out print the value the list.

26281.7 -> Alright, we are going to print it using I traitor dot next.

26287.7 -> Okay.

26288 -> So I've created two methods one is create a released for demo

26291.036 -> and the other one is print arraylist

26293 -> for demo create arraylist is doing nothing,

26295.5 -> but it's creating a list

26297.1 -> and it is returning the list

26299.012 -> and printer a demo is printing the list

26301.76 -> that you have passed as a parameter.

26304.2 -> Okay, so I create

26305.9 -> a new element of array list demo dot create arraylist.

26313.2 -> All right,

26314.2 -> and whatever I realize that I get over.

26317.5 -> Will is that I get I would be putting it here.

26323.4 -> Right now I create one more this and I print it.

26329.5 -> All right.

26330.1 -> Now when I print it I am going to pass

26332.546 -> this returned array list.

26334.2 -> All right, I think it's pretty clear now.

26336.513 -> So we have created a released in this method

26339 -> and we have returned it

26340.241 -> and in the second case we are just going to print it.

26343.3 -> We are going to take any array list

26345.35 -> and we are going to print it.

26347.056 -> All right.

26347.8 -> So let's see.

26349.3 -> So rest of the collections most

26351.248 -> of the collections you do it pretty much similarly.

26354.356 -> It's just that you know,

26355.848 -> it's used for different use cases.

26358.092 -> All right, I am getting some error I think okay.

26361.876 -> Yeah, you could see here.

26363.8 -> It has printed BMW Mercedes

26365.853 -> and Audi which we had put into the arraylist.

26369.2 -> Alright, so that's

26370.273 -> how you kind of I trade through it.

26372.4 -> Similarly.

26373.2 -> You could just remove it.

26374.9 -> You could use list I traitor

26377.3 -> Don't remove will remove the current element

26380.331 -> that's penetrated.

26381.7 -> All right.

26382.5 -> So yeah, this is I don't need to actually

26385.1 -> create one dot remove you could remove it.

26388.6 -> All right Drew.

26390.5 -> So that's how you remove it if you want to so you

26393.59 -> you have the same syntax.

26395.2 -> So basically we don't use I traitors nowadays more.

26398.578 -> It's more about we have Java 8 there are different constructs.

26402.7 -> Like we have Lambda expressions and stuff.

26405.3 -> We have screams stream processing,

26408 -> which is you have I traitors.

26411.1 -> All right.

26414 -> So this is what we have we have a hydrator,

26416.707 -> which is I creating through all the elements right

26419.59 -> and you could remove it as well using

26421.6 -> the I traitor usually nowadays.

26423.6 -> We use Java 8 streams

26425.5 -> which helps us to I'd rate through which is pretty much

26428.676 -> like the underneath is I traitor

26430.558 -> and stuff but there are some some kind

26432.735 -> of abstractions done

26433.82 -> so that we don't actually deal with

26435.67 -> I traitors there's some kind of abstractions

26438.2 -> are it's less verbose in this case.

26440.222 -> You have to write a lot of code to print through and everything.

26444.123 -> Whereas in streams.

26445.3 -> It would be just one method call

26447.4 -> which would do lot of things right.

26449.4 -> So that's what has been used as of now,

26452.2 -> but this should be good enough to start off with to understand

26455.5 -> the basics of it.

26456.6 -> Alright other thing is I was talking

26458.658 -> about the best practices.

26460.1 -> So it's good to have things broken down in methods.

26463.1 -> So that could reuse it rather than putting everything

26466.158 -> into the main method which makes it difficult

26469 -> for any other developers to understand mode.

26471.885 -> So basically it's a good practice.

26474.1 -> Make it modular,

26475.23 -> right and which enables reusability as well

26478.2 -> which reduces the lines of code within your program.

26481.7 -> So tomorrow if I have some other list,

26484.032 -> which I want to I trait I can just pass the list to this

26487.5 -> and it would right fit and give me the results.

26490.002 -> So I don't have to write the same piece of code again.

26492.864 -> Alright, so moving on

26494.1 -> so we have a released arraylist is nothing but abstraction done

26497.656 -> on a primitive array.

26498.923 -> So what are the advantages of using array list?

26501.7 -> It's more about it's faster

26503.5 -> in terms of retrieval right index based retrieval suppose.

26507.379 -> If you want to get to the index to just write

26510.374 -> like arraylist get

26511.6 -> to and it would give you the one at the end x

26513.8 -> 2 or the element at the index to whereas

26516.481 -> when it comes to insertions and deletions.

26519.3 -> If you want to insert a particular object

26522.4 -> at index 2 what it has to do is it has to move

26526.4 -> that was there at the index to to the index

26529 -> 3 and it has to increment the entire array by one

26532 -> or move to the right by Position which is pretty cumbersome,

26535.917 -> right which takes a lot of time so insertions

26538.585 -> and deletions are not good when it comes to arraylist,

26541.752 -> whereas when it comes to retrieval it's faster.

26544.5 -> So based on the use case you have to decide

26546.9 -> which data structure you should go for right?

26549.849 -> So simply put we think of Big Data applications.

26553 -> It's mostly about you don't have insertions and deletions

26556.455 -> as such it's not transaction,

26558.2 -> right but typical online transaction processing

26561.5 -> this thing would be application or say,

26564.1 -> for example, you have Amazon right Amazon or something

26567.217 -> where in you have a lot of transactions happening

26569.8 -> which needs insertions and deletions right

26572.4 -> in that case arraylist is not a good option.

26575.333 -> Whereas in terms of big data,

26577.244 -> which is like analytics right online analytical processing

26581 -> which doesn't have transactions as such right.

26583.447 -> It doesn't have insertions and deletions.

26585.8 -> It is one-time load you have data you load it

26588.335 -> into your data structures and you do some kind of processing

26591.6 -> or you do some kind of analytics on This data,

26594.9 -> but you don't manipulate this data.

26597.2 -> You don't actually have

26598.8 -> insertions or deletions done in such cases.

26601.599 -> It's better to go with a realist.

26603.7 -> All right, so

26604.448 -> which is a variant which is good for insertions and deletions

26607.978 -> that is linked list.

26609 -> All right, when it comes to insertions and deletions

26611.7 -> and you want to maintain

26612.9 -> the order of the list insertion order of the list.

26615.662 -> That's when you would go with linked lists.

26618.196 -> All right.

26618.8 -> So linked list is a sequence of Link's

26621.1 -> which contain items each link contains connection

26624.105 -> to another link and that's

26625.678 -> how insertions and deletions are simpler.

26628.1 -> You don't have to shift elements to the right

26630.3 -> when you insert it

26631.3 -> or you don't have to shift elements the left

26633.588 -> when you delete it.

26634.6 -> There are two types

26635.563 -> of linked lists to store element singly linked list

26638.1 -> and doubly linked list singly linked list is nothing

26640.9 -> but it has pointers

26642.017 -> in One Direction doubly linked list is

26643.911 -> like it has previous and the next its stores.

26646.586 -> Both each node would store previous element pointer to

26649.807 -> the previous element and the next element.

26652.7 -> So yeah, this is a singly linked list wherein you see

26655.3 -> that it has pointed to the next.

26657.5 -> It doesn't have pointed to the previous one, right?

26660.3 -> It's a one directional traversal, right?

26664 -> Whereas in doubly linked list,

26665.5 -> you could see that it is looping back

26667.3 -> to the previous element as well.

26668.925 -> So it has a pointer to the next

26670.5 -> and it has pointed to the previous one.

26672.8 -> It's a bi-directional traversal.

26675.3 -> So linked list has pretty much similar

26678 -> to arraylist you have ad you could add a particular object.

26682 -> You could check

26682.779 -> whether a particular object is contained within the linked list

26686 -> and that object has to be passed as a parameter to contains.

26689.3 -> You could add a certain element at a particular index.

26692.8 -> You could add it to the to the head of the list you

26695.3 -> could add to the last you could check the size of the list.

26699.048 -> You can remove the element from the list and you

26702.011 -> could get the index of a particular element

26704.624 -> so you could pass some element and get the index of it

26707.811 -> since linked list is again,

26709.458 -> it can have duplicate elements.

26711.387 -> If you want to get the last index

26713.353 -> of a particular element you could do that thing as well.

26716.607 -> So if you have multiple elements,

26718.5 -> you would get the last one right the index of the last one.

26722.1 -> So linked list example here you could see

26724.311 -> that a linked list of string is being created

26726.9 -> and you add values to it,

26728.8 -> which is fragile Rahul

26730.441 -> and Richard you add things to it.

26732.853 -> And and yeah,

26733.832 -> this is just about adding elements to the list.

26737.3 -> All right.

26738.8 -> So arraylist versus linked List released internally uses

26742.2 -> Dynamic array to store the elements since I said,

26745.158 -> it's Groove able it grows

26746.764 -> on its own linked list internally uses doubly

26749.582 -> linked list to store the elements to add an element

26752.815 -> in between or to remove an element

26755.064 -> from the array list slow

26756.7 -> because it internally uses array

26759 -> if any element is removed from the array list,

26761.7 -> then the rest of the elements should be shifted to the left.

26765 -> All right, similarly

26766.193 -> when you add something to the list you have

26768.7 -> to move everything to the right adding an element

26771.6 -> in between or removing

26772.7 -> an element with linked list is faster than arraylist

26775.7 -> because it uses doubly linked list.

26777.588 -> So no element shifting is required, right?

26780 -> You don't have to shift any address.

26781.822 -> Or something.

26782.5 -> It's just about moving the pointers.

26784.4 -> Right?

26784.9 -> So you would just move it skip one element

26787.498 -> and move to the next in terms of deletion.

26789.982 -> Whereas in terms of insertion,

26791.8 -> you would insert a node

26793.1 -> and you would manipulate

26794.3 -> the pointers according T. Alright arraylist

26797.4 -> can act as a list only it is normally for list

26801.8 -> but linked list could be thought of as a list as well as Q right

26806.3 -> since it's a doubly linked list you could have like first-in

26809.5 -> first-out arraylist is better for storing and accessing data.

26814.9 -> All right.

26815.557 -> So as I said,

26816.389 -> this is pretty much good enough for analytical sort

26819.5 -> of application analytical nature of application.

26822.4 -> Whereas when it comes

26823.635 -> to transactional linked list would be better.

26826 -> So linked list is better for manipulating data

26828.8 -> and it is slow in searching an element

26830.829 -> because it needs to compare the elements from the first note

26834.3 -> when it comes to you know,

26836.299 -> index based search.

26837.761 -> It is slower

26838.523 -> because it has to start all the way from the start.

26841.7 -> Was it goes through links?

26843.4 -> Right?

26843.762 -> It has links to next element and that's

26845.941 -> how it traverses through vectors are similar to erase

26850.1 -> but the Legacy form of it.

26851.9 -> It's a dynamic array again similar to arraylist.

26855.3 -> All right, it could be visualized very much

26858.2 -> similar to array list,

26859.999 -> but just that it's a legacy of java.

26862.8 -> It's not used to that extent

26864.7 -> or I would say it's not used at all at this point.

26868 -> But what is important to note is Vector is synchronized

26871.491 -> when it comes to multi-threading it's better to go with Vector,

26875.6 -> but nowadays we have concurrent arraylist arraylist

26879.095 -> that is supporting concurrency.

26881.3 -> So there are a lot of optimized versions of it

26884.248 -> which gives lot of performance Improvement.

26887 -> So vectors are no more used as such an industry.

26890.4 -> It's a Legacy form of arraylist.

26893.3 -> There are concurrent versions of arraylist

26895.931 -> that that has been evolved

26897.6 -> which could be used in multi-threaded applications.

26900.4 -> All right, Victor.

26901.759 -> Contain many Legacy methods

26903.8 -> that are not part of collections framework.

26906.442 -> So it doesn't even fit into collection framework

26909.4 -> because it contains some Legacy methods

26911.912 -> which are no longer used

26913.5 -> or which are not part of collection framework at all.

26917.4 -> Now Vector is again taken into collection framework

26921.246 -> and it implements list

26923.4 -> and that's the reason it has the implementation

26926.4 -> for this methods

26927.4 -> because this methods are typically coming from collection

26930.3 -> and list collection interface

26932 -> and list interface and all the concrete implementations

26935.425 -> have to implemented.

26936.638 -> And since Victor is

26937.756 -> one of the concrete implementations of list.

26940.352 -> They have to ensure

26941.5 -> that they Implement these methods as well.

26944.4 -> All right.

26944.953 -> So these are the methods pretty much similar to

26947.5 -> what we spoke earlier add clear and add

26950.3 -> to a particular index remove

26952.05 -> and then you could have size

26953.8 -> and you could have last index of and last index of object.

26957.6 -> So it's a vector of string then you add element you add.

26961.7 -> Issued fun and Kumar and you just write great

26964.822 -> through it to print out the message from a chiffon

26968.3 -> and Kumar would be the output of this application

26971.6 -> or this program.

26973.4 -> All right, so you could see I traitors use here as well.

26976.8 -> Like we did it in list.

26979.8 -> So let's talk about QQ is nothing but first in first

26983.2 -> out whatever goes

26984.34 -> in first would be first to come out a priority queue allows you

26988.5 -> to initialize the queue.

26990.2 -> These are implementations of Q.

26992.4 -> So you have a priority queue you have

26995 -> as we said linked list is list as well as Q so you

26998.6 -> could have linked list assigned to a queue right linked list

27003.9 -> is the list and linked list is a queue right is a relationship

27008.3 -> which means it's extending it right.

27011.1 -> So here we can see double ended queue lets you to a door

27015.8 -> and remove so double-ended interface DQ DQ interface

27020.743 -> allows you to Add

27022.1 -> and remove elements from Peak as well as from the bottom.

27025.6 -> That's what DQ is double ended queue,

27028.475 -> right and array d q is nothing but the concrete implementation

27032.5 -> of DQ EQ is an interface

27034.5 -> and the concrete implementation is array d

27037.3 -> q.

27038.1 -> So what are the Q & DQ methods you have ADD method

27041.9 -> which is nothing but it adds to the top of the queue

27045.2 -> and it returns a Boolean

27046.4 -> as you could see here if it is successful

27048.4 -> if it has added to the top of the queue

27050.933 -> it would give you true.

27052.5 -> And if not,

27053.284 -> then it would give you false right you have offer

27056.614 -> which inserts the specified element into the queue again,

27060.733 -> it does the similar stuff.

27062.6 -> It inserts to the cube.

27064.4 -> All right, you have removed

27066.1 -> which removes the head of the queue we have pull

27069.3 -> which retrieves and removes the head of the queue again.

27072.6 -> It does the same thing retrieves

27074.338 -> and removes the head of the queue and returns null

27077 -> if the queue is empty.

27078.4 -> All right, bullying is nothing but getting the top

27080.9 -> of the queue.

27081.8 -> And you have element

27083.9 -> which retrieves but does not remove.

27086.2 -> All right.

27086.7 -> So when you do Q dot element it would give you the top

27090.5 -> of the queue of the head of the queue,

27092.676 -> but it would just give you but it would still be there.

27095.577 -> So if you want to check value that is on the top of the queue

27099 -> if you want to check it

27100.352 -> and do something with it based on the value

27102.6 -> that is there on the top of the list or top of the queue.

27105.7 -> If you want to perform some actions we can do it

27108.4 -> using element Peak again does the same thing it retrieves

27111.7 -> but it does not remove the head of the queue

27114.1 -> if you want to actually retrieve and remove the head

27116.9 -> of the queue you would either use remove or pole.

27120.058 -> Basically you would use pole

27121.9 -> not remove right remove is not a good operation to do

27125.4 -> when you want to retrieve and do some actions on it.

27128.4 -> The best practice would be

27130.4 -> to use piec to retrieve and use Pole to actually retrieve

27135.8 -> and remove Alright,

27139.4 -> so let's take an example of Q.

27144.676 -> So right here in the package I create.

27149.9 -> Secretary main method, right?

27153.4 -> So I create private.

27157.4 -> Q v8q for demo All right,

27161.91 -> so it's asking me which Q I will go with this one,

27166.2 -> which is Java dot util dot Q.

27169.2 -> All right.

27169.5 -> Now I am creating

27170.5 -> a new priority queue which is a concrete implementation

27174.4 -> which would be say for example of integer, right?

27179.3 -> So I create a queue of integers.

27181.946 -> So we are putting integers within all right,

27185.6 -> and what we are doing is new.

27187.624 -> I am instance eating it.

27190.3 -> Alright, so this is a q

27192.2 -> which is going to hold just integers.

27194.4 -> That's what Jen Rick's come into picture, right?

27198.4 -> Queue of integers dot add suppose.

27201.1 -> I put a hundred and then I put ad could is used to

27206.4 -> as I said to insert right and I put 50.

27213.2 -> So I've created a queue and I written this Q.

27217.6 -> So I've created a q so far.

27219.611 -> Let me print this queue.

27222.569 -> Alright, so we have

27224.2 -> which is going to return void and print queue for demo

27231.2 -> and which is going to take you.

27233.6 -> All right Q of Cl you don't even put it here.

27240.9 -> I so now, let's see

27243.861 -> how we can retrieve elements from it one way is

27247.4 -> to I trade through it and let's see how pole

27250.882 -> and other things work right?

27254.492 -> So let me get the head of the list.

27259.1 -> So this is just retrieving it right retrieving

27261.999 -> head of the list.

27263.019 -> We are not removing it it is still there in the queue.

27266.2 -> We are just trying to check what it is.

27270.4 -> So when I say when it's retrieving it speak right now

27274.4 -> if I want to remove it

27276.1 -> if I want to kind of retrieve and remove it.

27281.5 -> So basically what I'm trying to say here is

27283.996 -> when you have q dot Peak it's going to return

27286.476 -> the top of the list which is nothing but 50.

27288.9 -> All right.

27289.6 -> So the first one the peak is just retrieving it.

27292.3 -> Whereas when I pull it it's going to retrieve

27295.712 -> and remove as well.

27297.8 -> So I have q dot pole is going to now

27303.8 -> when I do s out retrieve

27307.4 -> and remove Say this is the first attempt.

27313.1 -> All right, and we again do it which is the second attempt.

27317.3 -> This is just to show you

27318.813 -> that when you pull it it's actually removing it as well.

27322.281 -> Whereas Peak is not removing it.

27324.3 -> All right.

27325.5 -> So Peak is just retrieving it and this one is removing it.

27329.7 -> So the first pole is going to give you 50

27332.9 -> whereas the second pole is not going to give you 50.

27335.5 -> It's going to give you 200

27336.8 -> because it has removed 50 from the queue.

27338.8 -> All right, so this is what I wanted to show.

27341.2 -> So let me Q demo Alright, so here I'm going to do demo

27350.2 -> Dot.

27353.3 -> So when it comes to generic we can make this generic Q program

27357.6 -> by doing something of this

27359.485 -> and instead of hard-coding it you could put a Ste here.

27364.8 -> Right now, let's keep it as is.

27369.307 -> Alright, so the first case Q is being created the second case.

27374 -> We are going to see how we can pole works.

27378.9 -> Retrieving is just ringing

27380.7 -> and it is still keeping that element

27382.993 -> at the top of the queue

27384.5 -> whereas polling is actually removing it as well.

27388.8 -> All right, so you could see here Peak is giving you

27391.541 -> the last one here.

27392.6 -> It's a double-ended one.

27393.841 -> So it's giving you the last one here

27395.9 -> and pull is giving you this one.

27399.3 -> It's based on Friday.

27400.8 -> I think.

27402.4 -> All right, so you can see pole

27404.362 -> is giving you 50 as well and when you pull it again,

27408.2 -> it's giving you a hundred.

27410.9 -> All right, let's move on to the double ended queue.

27414.6 -> All right.

27415.3 -> So here we have something like you could remove first.

27419.1 -> All right, you know,

27420.2 -> so it's a double ended queue you could in fact

27422.8 -> in both the directions you you could actually

27425.521 -> remove first and add to the last

27427.3 -> and stuff like that.

27428.3 -> So you could see here

27430 -> that there's a double ended queue created

27432.6 -> with four elements initially 2142 63 and 84 and you could see

27438.769 -> that remove first is removing

27441 -> 4221 rather from here since 21 is the first one

27445 -> so it's removing 21 and remove lost or add

27448.746 -> last it's adding to the last

27450.9 -> which is nothing but it's adding hundred and five to the last

27455 -> So what is set is nothing but

27456.854 -> as we said it's a representation

27458.9 -> of mathematical set which is unique

27461.726 -> which holds unique values right?

27464.2 -> You cannot have duplicate values

27466.2 -> within set set has its implementation

27468.641 -> in various classes such as hashtag preset and linked

27472.1 -> as set so it's a mathematical set abstraction.

27476.1 -> We have variants of set in Java

27478.265 -> which is has said linked hash set

27480.5 -> and we said hash set is nothing but it hashes it

27484.1 -> or basically there's this indexing done

27487 -> and it's good for retrieval

27488.636 -> as you could imagine since it's indexed.

27491 -> It's good for retrieval.

27492.6 -> Okay.

27493 -> So the analogy

27494.2 -> behind this could be our it is analogous to index page

27498 -> that you have in books,

27499.559 -> right you have index page you just go

27501.949 -> to the index page and see at what page is the content

27505.4 -> that you are looking out for this one is

27507.7 -> pretty much similar to that.

27509.1 -> So when you do hashing you would be able

27511.6 -> to retrieve it much faster then sequential retrieval.

27515.6 -> All right, so that's

27516.835 -> what has said does and it has unique values of course,

27520.098 -> which is a property of a set.

27521.848 -> You can't have multiple values within

27524.099 -> or duplicate values within it doesn't sort automatically.

27527.6 -> This is a typo here has set is

27530.6 -> acid doesn't maintain maintain any order

27533.6 -> at all its internal to The order

27536.4 -> in which the retrieval would be done is pretty much internal

27539.4 -> to the runtime or what I mean to say is

27541.635 -> if you have a has set with the same content

27544.128 -> and if you run it multiple times you would see

27546.8 -> that the retrieval is different in different instances.

27550.5 -> So it doesn't maintain any order your application

27554 -> might demand something or demand a data structure

27557.2 -> that is set as well as it maintains just

27559.9 -> the insertion order right?

27562.2 -> That's a scenario

27563.2 -> in which you would go with linked hash set.

27566 -> So link -

27566.8 -> there is nothing but set which has

27569.275 -> its insertion order maintained.

27572 -> All right.

27572.7 -> So the third one is tree set,

27575.03 -> which is nothing but it

27577 -> so these are the methods that gets inherited

27579.58 -> into hash set and but similar to other collections

27582.594 -> that we have,

27583.423 -> but just to talk about this one

27585.4 -> so you have ad which is just adding object into hazard

27590.1 -> or linked has set you have contains

27592.9 -> which is basically checking

27594.591 -> whether a particular.

27595.811 -> Object is present in a set.

27597.4 -> You can clear the contents of the set.

27599.365 -> You can check

27600.061 -> whether a set is empty using he's empty method.

27602.541 -> You can remove a particular object from a set using

27605.247 -> remove method and pass.

27606.6 -> The object that you want to remove clone

27608.927 -> is nothing but a method

27610.3 -> that is inherited from object class,

27612.8 -> which is super class

27614.1 -> and it is basically meant for cloning any data structure

27617.727 -> or any class or any instance of a class.

27620.511 -> All right.

27621.2 -> So when I say cloning it's not but making a copy of it

27625.1 -> and it's a shallow copy.

27626.7 -> There is a steep coffee

27628 -> and there's a shallow copy shallow copy is nothing

27630.6 -> but the properties within the set.

27632.8 -> So the references remain the same basically you

27635.8 -> would have a value say for example string right?

27639.028 -> If you have a value say at Eureka you would basically

27642.7 -> have both the set pointing to the same instance of a dareka.

27647.3 -> All right.

27647.868 -> So it's a shallow copy and deep copies were

27650.3 -> in you would have different instances or together.

27653.4 -> So when A Change Is Made in new set A particular element

27657.5 -> it won't be reflected in the other set.

27659.4 -> So that's deep copy,

27660.717 -> but by default the shallow copy that's done.

27663.5 -> If you want to deep

27664.683 -> copied then you will have to use some other utility

27667.8 -> or you some other class.

27669.362 -> All right, there's an iterator similar to other collection

27673.046 -> you can have I traitor to iterate through the set

27676.042 -> and if you want to check

27677.54 -> the size of the set you could use the size method.

27680.7 -> All right.

27681.782 -> So let's see an example of hash set and linked has set.

27686.1 -> Alright, so here I have created two methods create hash set

27691.2 -> which creates the instance of has set and add

27694.405 -> some integer values to it,

27696.3 -> which is 130 340 and 440

27698.2 -> and you see there is one more method created

27701.5 -> which is create linked hash set

27703.526 -> which is again inserting three elements into it,

27706.6 -> which is hundred three hundred and five one.

27709 -> So I return this.

27711 -> All right now I write a method to 848 through it.

27715.7 -> Which is displaying nothing

27717.776 -> and Print set and which would hit s.

27724.7 -> All right.

27725.8 -> What you do is you have like set

27728.6 -> to print dot you could have I traitor right

27732.1 -> which would give you I traitor

27733.943 -> which would give you an instance of I traitor for set.

27739.3 -> Alright, so we have I traitor created for set now.

27742.279 -> Let's iterate through it.

27746.5 -> so remember how we I treated list

27749.7 -> so you would say set I traitor dot has next

27753.784 -> if it has next then print the value

27756.4 -> of So basically we have this

27762 -> then you have set I traitor dot next

27765.9 -> which would give you the actual value.

27769.3 -> Alright, so we have a method

27771.22 -> which would I trade through the set

27773.553 -> and display its content?

27775.9 -> All right.

27776.6 -> Now what I do is I create instance of set demo.

27785.1 -> I create has set and whatever value I get.

27788.9 -> I put it as as set.

27792.6 -> That's it for demo.

27795.8 -> All right, keep it I set.

27797.8 -> All right.

27799.1 -> Now I have against it.

27801.692 -> I say linked has set for demo.

27804 -> So basically we just creating the set.

27807.9 -> All right, then we create the linked hash set now said

27812.197 -> demo we are going to print it.

27814.588 -> The first one to be printed is is Hash set for demo.

27818.8 -> And this is what is reusable ET right?

27821.565 -> See I'm not fighting the method to print it multiple times.

27825.9 -> It's just once and which could be used

27828.4 -> for printing has set as well as linked has sit.

27832.1 -> So this is what reusability is all about.

27834.5 -> If you don't expose it as a method and

27836.7 -> if you write it within your main method,

27838.667 -> you won't be able to reuse it

27840.213 -> and you would have to write the same piece

27842.4 -> of code multiple times

27843.751 -> which adds to the redundancy and which is not a good practice.

27848.2 -> And this also makes it much more readable by looking at it.

27852.1 -> You can understand that.

27853.312 -> Okay, it's creating a hazard.

27854.856 -> The second method is creating a link has said

27857.2 -> and the third one is printing asset.

27859.1 -> So it makes much more readable, right?

27861.457 -> So that's an important factor as well

27863.751 -> when it comes to programming.

27866.2 -> Alright, so here we can see

27868.2 -> that when I printed the hash set it gave me 133 4440.

27872.4 -> Now the thing is it's just three elements.

27874.677 -> So it has maintained the insertion order.

27876.9 -> But basically if I have more elements you can just

27880.1 -> copy this multiple.

27882.8 -> Okay, I remove this.

27887.9 -> Okay.

27888.517 -> Now you can see

27889.373 -> that you won't get it in insertion order

27891.6 -> since it was it was just three elements

27894.294 -> its by fluke

27895.217 -> that you got it in the same order as which you inserted.

27899.942 -> So if you see it now.

27902.7 -> So now you can see that,

27904.351 -> you know, the first element that got retrieved is 4401

27908 -> which was basically you put it at the last ride.

27911.275 -> So it's pretty much random.

27913.053 -> As I said linked has set.

27914.7 -> The retrieval would be pretty much random.

27917 -> You could see 4401 then 130 which was the first element

27921.6 -> inserted than 340 then 440 then you saw 40,

27925.1 -> which is again out of order.

27927.261 -> So basically this is

27928.8 -> what linked has said does and suppose I put

27932.2 -> the same values in the link has set you would see

27935.7 -> that insertion order is maintained.

27937.8 -> All right, so from here

27940.5 -> if you see from 130 in from here,

27943.7 -> it's printing linked has it

27945.556 -> and you could see the insertion order being maintained

27949.2 -> as is 4410 and when you see Hazard,

27953.5 -> which is very much like this one,

27955.1 -> you can see that it's random.

27957.089 -> All right, so

27958.027 -> that's what link has set an asset differs own

27961.2 -> preset is nothing,

27962.524 -> but it Sorted set

27963.741 -> and you have a retain all method retain all method is

27967.4 -> nothing but intersection between two sets.

27970.238 -> So basically you could pass one more set

27972.814 -> to the retain all method

27974.4 -> and you would get an intersection of two sets.

27977.2 -> So what I mean to say is if you set has value one,

27980.8 -> two, one, two,

27981.9 -> three four and you pass one more set to it

27985.1 -> or you invoke retain all method and pass one more set to it

27989.561 -> which has values 1 and 2.

27991.9 -> All right.

27992.7 -> So your Source set on which retain all method

27995.895 -> is being called that has got four elements 1 2 3 & 4

27999.6 -> whereas the set

28000.45 -> that is passed to retain all contains only two elements.

28003.566 -> That is one and two.

28004.7 -> All right.

28005.2 -> Now when you invoke it your Source will have only

28008.4 -> one and two your 3 & 4 would be removed off

28011.222 -> from the source set

28012.5 -> because the retinol method is nothing but it's an intersection

28016.6 -> between two sets.

28018 -> Okay?

28019.5 -> So size and hashcode,

28022.373 -> so all these methods remain the same as other ones

28026.142 -> that you have in different collections, right?

28029.7 -> So you have like size which would give you size.

28032.671 -> Hash code is nothing but a unique integer

28035.2 -> that's written for any object in Java.

28037.827 -> It's not just free set.

28039.386 -> Any object in Java when you invoke hashcode,

28042.5 -> it would give unique integer.

28044.3 -> All right,

28045 -> because this particular method is inherited from object class

28049.1 -> of java contains is nothing

28051.1 -> but pretty much similar you pass element and check

28053.723 -> whether that element

28054.9 -> is contained in the source set contains.

28057.6 -> All is something like retain all it would return true only

28061.7 -> if all the elements in the collection

28064 -> that's passed here

28065.2 -> as an argument is present in the source set.

28068.6 -> All right, it has to have everything all the elements.

28071.832 -> So the previous case wherein I said the source has one two,

28075.481 -> three and four and if you do collect contains all

28078.5 -> on a set Are you pass a set to contains all

28081.317 -> with values 1 and 2

28082.591 -> it would return true.

28084.138 -> Whereas if you pass a collection

28086.6 -> with values 5 & 6 it would say false

28089.8 -> because you don't have values 5 & 6 in your Source collection.

28094 -> All right, I traitor is nothing but it Returns the iterator

28097 -> that we checked on you

28098.6 -> can convert it

28099.6 -> to to array any collection could be converted to to array

28102.8 -> which would give you object array.

28105.282 -> You could check equals basically checks

28108.261 -> if the collection is I think it has to be empty

28111.8 -> here it checks whether your collection is empty.

28115.7 -> So there's a typo here.

28118.8 -> Just to give you an example.

28120.8 -> I will create one more.

28124 -> So I copied the same method and I said create rehash set.

28129.8 -> All right.

28130.6 -> So what I do here is I will make these changes.

28133.743 -> I will keep it

28134.7 -> as this could be kept as set and this is like free.

28141.3 -> All right, so tree set and and we are set.

28148.1 -> Now I print this one.

28151 -> Okay, basically set the dough dot create rehash set.

28157.5 -> All right, so I'm printing this so prior to that.

28161.3 -> Maybe I will put a statement here printing stre set.

28168.83 -> All right, so I created a tree set with this random values

28172.3 -> 133 4440 and stuff like that.

28174.9 -> Now let's check whether it has sorted it or not.

28178 -> Right?

28178.7 -> So I created a tree set and I'm just printing it here.

28182.7 -> So what you can see here there's we have created reset now

28188.8 -> if you see it right

28190.258 -> after printing tree set all the values

28193.1 -> that you see here then 3044 41 3440.

28198.2 -> It's all sorted efficiency.

28200.104 -> Right and it's Unique as well.

28202.2 -> So if you insert it multiple times like

28204.835 -> if you insert

28205.742 -> n multiple times still in it would take Just one value of 10.

28209.929 -> All right, so you cannot have multiple values

28213.4 -> if you put 10 unlike array list or linked list,

28216.9 -> which will have multiple values.

28218.926 -> This would take just one 10.

28220.7 -> All right, it would ignore the other one.

28223.6 -> Enunciate is a special type of set which creates genome

28227.3 -> is nothing but a constant it's a replacement

28230.01 -> for constant in Java.

28231.42 -> So basically the replacement

28233.3 -> for public static final and basically

28236 -> for constant earlier.

28237.559 -> It was like we used to use public static final

28240.9 -> but now it's advisable to use enums four constants.

28245.2 -> All right, we'll see an example

28246.7 -> which would give you much more clear idea about it.

28249.2 -> So first one is all of all of method is nothing

28252.302 -> but creates an enum set containing all of the elements

28255.876 -> in the specified element type.

28257.9 -> So it would create enum set with all of the elements

28261.923 -> that you have copy

28263.287 -> of is nothing but creates an enum set initialized

28266.802 -> from the specified collection.

28269 -> All right, so you could pass a collection

28271.074 -> and it would create an enum set out of it.

28273.276 -> None of is creates a MD enum set with the specified element type

28278.4 -> or this creates a in mm

28280.5 -> set initially containing the specified element.

28283.9 -> Can you could initialize it as well?

28286.2 -> So basically here we

28287.9 -> are giving a specific class with which it would be created

28291.8 -> or the enum set would be created range creates a enum

28295.8 -> set initially containing the specified elements,

28300.2 -> right and clone is nothing.

28302.8 -> But again, it's pretty much similar.

28305.1 -> As I said clone is a is a method

28307.524 -> that is inherited from object class

28309.982 -> and is meant to clone

28311.5 -> or have a shallow copy of the data structure

28314.2 -> against which it is invoked or object against which it

28317.766 -> which the Clone method is invoked.

28319.8 -> All right.

28321.3 -> So here we can see there's the enum

28323.5 -> which is months.

28325.1 -> Alright, so here you could see a in a months

28327.801 -> which has like three months declared

28330 -> within Jan Feb and March.

28332 -> All right.

28332.5 -> So now what you do is, you know him set off

28335.695 -> and you just wait set out of two of these elements,

28339.5 -> which is Fab and March.

28341.3 -> All right, so this is what Them office

28344.2 -> so you could have

28345.348 -> some enum values put in and it would create set out of it.

28349.2 -> Now when you write rate through it,

28351.3 -> you would see that you have Fab

28353.6 -> and March into your genome set.

28357 -> All right.

28357.496 -> So this is something that is required

28359.315 -> when you have enums with multiple constants

28361.446 -> and if you want to have

28362.798 -> or you want to create set out of it and do something

28365.4 -> with it, right?

28366.5 -> So it would be pretty much common

28368.9 -> or you imagine of enums as exhaustive list of constants,

28374.3 -> right which is used throughout your application.

28376.8 -> Now there might be instances

28378.527 -> where in you want to have you want to put them into set

28381.938 -> and do something with it.

28383.523 -> Right?

28384.1 -> So basically this is mint

28386 -> because the values within your enum cannot be put

28389.41 -> into a data structure as of now or prepare to enum set.

28393.363 -> We were not able to put the values within the enums

28396.926 -> into a data structure, right?

28398.992 -> It was considered as a separate entity.

28401.8 -> So now this is

28403.4 -> That you could put it into a data structure as object

28406.9 -> and you could play around with it.

28408.88 -> So that's the reason we have enum set.

28411.6 -> What is map map is nothing but it's a key/value pair

28415.215 -> and it is unique Keys you it holds unique keys.

28418.389 -> So suppose if you try to insert same key with different value,

28422.7 -> you would have your value updated

28424.653 -> or overwritten with the new one.

28426.747 -> All right, so

28427.531 -> but it won't duplicate it.

28429.146 -> So what I mean to say is it maintains a key value pair,

28432.7 -> but the key is going to be unique across.

28435.7 -> All right.

28436.2 -> So This Could Be Imagined as a table, right?

28438.729 -> You have a table in data structure,

28440.7 -> which has got one primary key say employee ID

28443.751 -> and there's a name

28445 -> which is like name of the employee right?

28448 -> Imagine.

28448.4 -> This ID is a primary key, right?

28451.3 -> So you cannot have multiple values.

28453.3 -> So if you try to put some multiple

28455.379 -> if you try to put one more value to it,

28457.772 -> it won't allow you to put in.

28459.6 -> The only thing that you could do is update the value

28462.4 -> of existing ideas.

28463.7 -> He's our add a new ID.

28465.8 -> So this is pretty much similar to that.

28468 -> Right map is specifically for maintaining key value pair

28471.856 -> and we're in Keys would be unique

28473.995 -> and if you try to map

28475.4 -> and existing key with a new value,

28477.4 -> you would see that the value is been overwritten,

28479.9 -> but you won't have to kick it keys.

28481.9 -> Right again.

28483.1 -> There are different variants

28484.6 -> that we would look at map has hash map

28487.2 -> which is similar to Hash set

28489.267 -> which is based on indexing or hashing.

28492.1 -> All right, you have linked hash map,

28493.976 -> which is pretty much similar again.

28495.8 -> Hashmap doesn't maintain the sequence of insertions

28499.017 -> linked hashmap maintains the sequence of insertions.

28502.3 -> There is a sorted map which is again free map

28505.8 -> and which is sorted on based on Keys.

28509.4 -> All right.

28509.988 -> So the structure

28510.971 -> that you see here is pretty much similar to set

28513.8 -> right we had hash set

28515.3 -> we had linked hash set and we had preset

28518.105 -> so this one is pretty much on the same lines

28521.2 -> as set So how do you put data into your hash map?

28525.5 -> It's with put method,

28526.977 -> right you have put method and you you put some key and value.

28531.3 -> All right, we have put all we can have an existing map.

28534.9 -> And if you want to put all the key value pairs

28537.4 -> that they're into a map into a new map,

28539.7 -> you could use put all or you could remove some key.

28543.5 -> You could get some key.

28545.2 -> All right, you could check

28547 -> whether a particular key is contained within hashmap.

28550.184 -> You could get your key all the keys

28552.8 -> in the hashmap as a set,

28555 -> which is key set give you extract all the keys

28558.2 -> as set and as their unique already,

28560.688 -> then you would get a new set returned out

28563.531 -> from he said entry said

28565.184 -> Returns the set view containing all key value keys and values.

28569.692 -> So basically you would get all the keys

28572.5 -> and values as a set

28574.1 -> when it comes to entry set

28575.582 -> from the entry said you could get key

28577.7 -> and value distinctly.

28579.5 -> All right, so get key is nothing but obtained

28583.1 -> a key get value would give you a value against the key.

28587.1 -> Now.

28587.3 -> What are the typical exceptions

28588.8 -> that you get when you deal with map some exceptions Throne

28592.3 -> while using map interface is no such element exception.

28595.7 -> So when you are trying to invoke some item from the map

28598.4 -> if you're trying to invoke a key that doesn't exist.

28601.4 -> This is what you would get.

28602.9 -> Okay, this is more about when there are no items

28605.8 -> if there is no item that exists in the map at all

28609 -> if it's an empty one,

28610.2 -> and if you are trying to retrieve something

28612.458 -> that's when you would get no such element exception.

28615.4 -> All right Class cast exception is pretty much.

28618.204 -> It's a generic exception

28619.7 -> that you get when you try to cast it against an object

28623.577 -> or suppose value is a string.

28625.7 -> All right, and if you try to cast it to integer you

28628.417 -> would get a Class cast exception

28630.3 -> since string cannot be mapped into integer.

28633.8 -> All right.

28634.8 -> Now pointer exception is the runtime exception

28637.848 -> which we saw that

28639 -> if You haven't initialized your hash map.

28641.9 -> And if you try to put something into it,

28644.2 -> you would get null pointer exception.

28646 -> So you have to make sure

28647.2 -> that you instantiate the map first

28649.7 -> and then start using it unsupported operation exception.

28653.985 -> This occurs when an attempt

28655.944 -> is made to change a map which is unmodified unmodifiable.

28659.895 -> So you can get unmodifiable version of a map.

28663 -> And if you try to change something within it this is

28665.735 -> what you are going to get unsupported operation.

28669.703 -> Hashmap linked hashmap and free map.

28672.9 -> So this is pretty much similar to the examples

28675.547 -> that we saw

28676.3 -> for the set write Java hashmap class implements

28680.092 -> the map interface by using hash tables.

28683.161 -> It inherits abstract map and implements map interface.

28687.4 -> It contains only unique elements hash map contains

28691.326 -> values based on the key.

28693.569 -> It may have multiple null values,

28696.253 -> but only one real key.

28698.3 -> So this is important to note.

28699.892 -> You can have multiple null values.

28701.8 -> But only in one alky you can't have multiple

28704.5 -> in alkies sonal is also treated as a key as a valid key

28708.9 -> when it comes to hashmap, right?

28711.021 -> Whereas in hash table

28712.433 -> this one more variant of key-value pair,

28715.055 -> which is Hash table,

28716.4 -> which would throw you an error if you have G as null

28719.715 -> but hashmap take ski as null so that's an advantage of it.

28724.1 -> So hash map doesn't maintain the order of the element

28727.3 -> linked hashmap maintains the order of the elements.

28729.8 -> In which they were entered

28731.292 -> and treemap sorts based on the key.

28734.8 -> So these are pretty much the same thing

28737.2 -> that we discussed for map earlier.

28739.4 -> If you see entry set key set and all those things

28742.6 -> we have already discussed about and it's the same this something

28747.312 -> that we have in specific to tree map.

28750 -> You could get first key.

28751.736 -> You could get lost key.

28753.4 -> All right,

28754.2 -> since it is sorted you could get it now.

28757.633 -> There's a hashmap example.

28768.4 -> I create a main method first.

28770.6 -> Then I create private map and then create.

28777.4 -> hashmap And I create a new map here

28782.2 -> say app of integer string.

28788 -> Typically you would have integer as your ID right employ map.

28795.2 -> All right, and which would be new suppose.

28798.101 -> I create a new hash map.

28801.6 -> Read so I'm creating a new map here,

28803.933 -> which is like the key

28805.333 -> would be integer your value would be string.

28810 -> not put Buddhism method

28812.5 -> that we use and say employ map dot put Alright,

28818.1 -> so this is how you put into it put into map.

28821 -> All right, so I'd written this map from here.

28823.9 -> So we so we'll take an example of hash map.

28827.3 -> Where in we would be putting some ID

28829.706 -> and we would be putting some value as a string

28833.1 -> and we would check

28834.4 -> how it gets I treated

28835.903 -> or how we can hydrate through or get something out of the set

28840.2 -> out of the map.

28841.5 -> Okay.

28842.3 -> So here you can see that I created a hashmap.

28845.5 -> I created this method

28846.756 -> which is create hashmap and I put some value

28849.319 -> within which is nothing but and you could see here.

28852.4 -> It's a map of integer and string.

28854.5 -> So I put a value of one

28856.6 -> and I put value as X I put 2 and value

28860.346 -> as Y and I put a hundred and value as a right.

28864 -> So I created a map of employee ID and employ name

28868.434 -> so to say right?

28870 -> Okay, so I've created this

28872.6 -> and so what we are going to do here

28874.6 -> is so you could even print out a map.

28877.673 -> See if you want

28878.826 -> if I print it out like this like map to print you would see all

28884.7 -> the values contained within the map.

28887.392 -> All right, so this is all right.

28889.846 -> I print the hash map right here.

28892.303 -> So basically I created demo dot create hashmap.

28897.5 -> Okay, demo dot print map and let's print this map here.

28903.9 -> All right, so we have inserted three entries into this map 12

28909.1 -> and hundred with ID 1 to 100 and which has got value of XY

28914.8 -> and a respectively

28918.1 -> And what we are doing is we are just printing the map contains

28921.7 -> of the map right here.

28923.465 -> So you could see here is 1/2 and hundred been printed out here.

28928.4 -> Alright.

28929.3 -> So again, this is a hash map

28931.3 -> and you could have it's based on hashing.

28934.611 -> So it doesn't maintain any order.

28936.7 -> So if you have multiple values within you would see

28940.352 -> that the order is not maintained similar

28943.2 -> to what we had in hashmap.

28945.4 -> So if I put something like this Alright

28948.7 -> now when I run it you would see

28950.523 -> that insertion order is not being maintained

28952.929 -> and when you retrieve it,

28954.4 -> you will get it in any order.

28957.1 -> All right here we can see that the order

28960.6 -> is not been maintained 112 is displayed first,

28963.42 -> which is second last actually.

28965.3 -> All right, so it gives you all the entries within the map

28968.594 -> but it won't maintain the insertion order.

28970.7 -> So that's if you want

28972 -> to maintain the insertion order you have used linked hashmap.

28975 -> All right,

28976.1 -> if I change this to link to map linked hashmap just

28980.874 -> one single change would sigh copy the same stuff here.

28985.1 -> All right, and I put a link hashmap.

28988.6 -> All right and suppose I create one more which is 43 map.

28997.3 -> All right, so we have created three Maps

28999.7 -> here one is your tree map.

29001.8 -> So the other one is linked hashmap link - map now.

29007.6 -> Let's print one by one, right?

29010 -> The first one is hashmap that's already been printed here.

29013.9 -> Now, I create linked hashmap.

29017.2 -> Right?

29018 -> And the third one that I print is demo dot create remap.

29024.7 -> All right, so we have all the three maps created

29028.382 -> and we are printing it here.

29030.8 -> Alright, so here you could see that when it comes to hashmap.

29035.6 -> The key value pair is not maintained.

29037.717 -> Right?

29038.517 -> Whereas when it comes to link the hashmap.

29041 -> This is a link hashmap and you could see

29043.5 -> that the order is exactly the same as the order

29046.613 -> in which we put in.

29047.9 -> All right, and when it comes

29050.6 -> to tree map with the third one and here you can see

29054.7 -> that it's sorted one.

29056.4 -> So sorted by your key.

29058.623 -> Not the value.

29059.7 -> Alright, so see the key to the left hand side

29061.9 -> when it says 1 equal to X1 is the key and X is the value

29066.261 -> if you see it will see that

29068.338 -> 12 Levin 2,100 hundred and eleven hundred

29072.4 -> and twelve 1010 and 1100

29075.6 -> so you could see that it's been sorted / the key.

29080.7 -> All right.

29081.2 -> So this genome map

29083.169 -> in a map with specialized map implementation for enum Keys.

29087.9 -> All right, which we saw here.

29090.2 -> We can see that there is a enum which is nothing but constants

29093.788 -> and you could see three constants been put

29096.026 -> into the months,

29096.9 -> which is Jan Feb and March

29098.9 -> and you could see here is a in a map created

29102.232 -> for all the months or for all the months

29105.6 -> that you have within your genome

29107.9 -> that is months right you have this in a map

29111.8 -> and you could actually put in values something like this.

29115.6 -> So basically in a map is nothing but you could use the enums

29119.982 -> or the value within the enums as your keys.

29123.1 -> All right, when you use in a maps and you

29125.8 -> could just write rate through it to see

29128.211 -> that you know,

29129.1 -> you have this Keys put in and values put in properly.

29133.1 -> All right.

29133.6 -> So, so just to give you an example we can have

29141.461 -> we can create an enum here.

29145.2 -> I'll choose to create them same one

29148.192 -> and I create enum here, right?

29150.5 -> So I create in a month and which has got say for example,

29154.6 -> Jan Feb March.

29156.8 -> All right, so we have created this now

29159.646 -> what I do is I create a new in a map with months

29163.6 -> and with string as its value,

29166.819 -> so I create a main.

29170.9 -> Gina map fifth month

29173.5 -> and maybe we could put into your head.

29176.723 -> I create this in a map here.

29179.6 -> All right in a map of our you have month and integer.

29189.5 -> Alright, so here we will have to give a month dot

29195.946 -> or even months.

29197.1 -> Okay?

29198.8 -> Ticks class 1 class.

29202.4 -> All right.

29203.5 -> So in the Constructor we could see that it takes

29206.4 -> class as a parameter.

29208 -> So we put one thought class as a parameter now I put ma'am

29212.384 -> don't put I put like the the key

29219.7 -> is your it is depicting something

29224.2 -> like seals ton per month.

29226.8 -> All right it basically it refrains you

29229.8 -> from putting anything but the enum value as your key.

29234.3 -> All right, so that's

29235.3 -> what we are trying to do here and you could just print.

29241.1 -> In a map calendar

29242.5 -> and you should be able to see the values.

29244.8 -> All right, so it's basically restricting the key as one

29248.384 -> of the values or one of the constants declared

29251.371 -> within your enum.

29254.2 -> See how you can see here.

29255.782 -> Jan is equal to hundred fehb is equal to 200 you could.

29260.5 -> Now I will quickly talk about comparable and comparator

29263.5 -> comparable and comparator are the two interfaces or it's used

29267.9 -> when you want to have sorted set

29269.9 -> or if you want to sort a collection say for example,

29272.9 -> you have lists of integer

29274.305 -> and you want to sort it a list of integer is something

29277.423 -> that is by default could be done

29279.3 -> because integer itself implements comparator,

29282.241 -> but if you have a self-defined class

29284.5 -> or if you have your own class say for example,

29287.4 -> if you have your own defined class something

29290.592 -> like this vehicle info,

29292.32 -> which has like a number of Wheels mileage and name

29296 -> of the vehicle put in now

29298 -> if you want to sort this particular class

29300 -> if you give it to a sorter,

29301.569 -> it won't understand

29302.652 -> because this is a self-defined class straight.

29305.3 -> It won't understand

29306.417 -> what you want to sort in this right.

29308.4 -> Basically when you have something of this sort

29310.6 -> when you have your own defined class and you want to sort it,

29313.9 -> that's when you use some variable and comparator.

29316.7 -> All right, so I'll just walk you through it so comparable.

29320.5 -> Phase is used to sort

29321.9 -> the objects of user-defined class in an order.

29325.1 -> So to give you an example

29326.9 -> suppose you have an employee class

29329 -> which has got ID and say salary, right?

29331.9 -> If you want to sort it by default.

29334.2 -> Java wouldn't know

29335.1 -> what you want to sort within that particular class, right?

29338.1 -> You want to sort it by the identifier

29340.2 -> or the ID field within the employ

29342.5 -> or if that's the use case,

29344.2 -> then it could be

29345 -> like you want to understand the order in which employees

29348.407 -> joined the company and the other case.

29351.049 -> Could you want to sort it by salary to understand

29354.018 -> which employees taking the most salary

29356.352 -> or to understand the sequence

29358.254 -> in which salaries been paid to the employees, right?

29361.53 -> So to make Java understand

29363.2 -> which use case you are trying to solve

29365.4 -> based on which identifier

29367.282 -> or based on which property

29369.2 -> or instance variable within your class.

29371.9 -> You want to sort to just indicate Java

29374.5 -> that this is what we want to do express it

29377.1 -> in a form of implementing comparable interface.

29380.3 -> It is in Java dot length package and it contains only one method

29384.337 -> that is compared to it provides single sorting sequence only

29388.1 -> that is you can sort the elements based

29390.6 -> on one data only you can't have multiple data consort based

29394.621 -> on multiple data.

29395.8 -> All right.

29397.9 -> So I'll just walk you through this

29399.9 -> which would give you an example.

29401.9 -> So so basically you have a student

29404.4 -> which implements comparable now here you could relate

29407.766 -> to the example

29408.59 -> that I took wherein you have roll number

29410.884 -> and name now you want to sort it.

29412.7 -> Now what we are trying to sort here is by rule number.

29415.7 -> So that's how you express using comparable.

29418.2 -> Right?

29418.5 -> You have comparable student, right?

29421.5 -> And you could see here.

29423.2 -> There's a compareto method

29424.847 -> that this comparable student has got all the comparable interface

29428.9 -> has got now compared to will take student as a parameter.

29433.1 -> All right.

29433.823 -> Now you could see

29434.99 -> that we are comparing rule number right

29437.7 -> you're comparing the rule number of the parameter student

29441.2 -> that's been passed to the compared to

29443.4 -> if it is equal then it's 0

29445.6 -> right you don't have to do anything

29448.2 -> if it is greater,

29449.3 -> then you written as 1 and

29451.016 -> if it is less then you return as minus 1 so basically based

29455 -> on this compared to Java will do sorting All right,

29458.6 -> it will sort it based on whatever you provide here.

29461.7 -> So what you are trying to tell Java is

29463.912 -> if it is equal we are returning 0 so this is a contract.

29467.384 -> Okay.

29467.7 -> This is what we need to actually this is

29470.365 -> how it's been coded or this is a contract

29473.1 -> that you need to follow whenever you compare to.

29475.7 -> So if it is a real number then you say it's

29479.079 -> rule number 0 or return 0 if if both the real numbers match

29483.6 -> if the one in your instance is greater

29486 -> than the one being passed here.

29487.9 -> Then it would written one or else - one.

29490.8 -> All right.

29491.702 -> So how do we use this?

29493.5 -> So basically you can see here you created student.

29497.63 -> All right, so they were

29499.4 -> like three students created 101103 and 102.

29503.234 -> You could see three IDs being created here.

29506.465 -> All right.

29507.3 -> Now what you're doing here is collections dot sort

29511.5 -> and you're passing your array list of student

29515.2 -> and you use collections dots

29517.6 -> Not right when you do collections dot sort

29520.2 -> what it would do is it would arrange it

29522.8 -> or it would sort the array the order of rule number so 1 0

29527.78 -> 1 would be first 102 would be second

29530.479 -> and 103 would be the last.

29534.1 -> All right, so there's comparable and this comparator.

29537.8 -> All right.

29538.3 -> There are two interfaces comparator is nothing

29541.088 -> but it is used to order the object of use again.

29544 -> It is used to order the object of user-defined class.

29547.684 -> But what is different

29549.3 -> in comparable is comparable takes compared

29552.5 -> to which takes just one parameter as input

29555.7 -> and the other parameter is nothing but the instance

29558.808 -> within the class itself.

29560.3 -> All right,

29560.8 -> although this instance rather the instance

29563.59 -> on which this particular method

29565.7 -> or instance on which compareto method was called.

29569.6 -> All right.

29570.229 -> So basically comparable will have only one method

29573.923 -> compared to all right,

29575.505 -> whereas comparator

29576.8 -> when you use comparator interface it will it

29579.654 -> will take two methods

29580.99 -> or it will take two parameters in the compare method.

29584.3 -> All right, and it will compare both the parameters

29587.3 -> that are passed.

29588.5 -> So basically it's

29589.618 -> for customized sorting in the first example,

29592.906 -> that is comparable.

29594.2 -> We are putting the logic of comparing

29596.748 -> within the class itself,

29598.478 -> but you have a separate class

29600.568 -> which implements this particular comparison logic.

29604.8 -> So basically you could see here right you have a class student

29608.824 -> and student is just holding the values of roll number name.

29612.561 -> All right, you don't see

29614.107 -> how you don't see the comparison logic with them.

29617.276 -> Now you have another class which is named comparator

29621.2 -> which implements comparator.

29623.7 -> Alright this name comparator which implements comparator now

29627.81 -> if you see the compare method,

29629.9 -> it takes two parameters,

29632.5 -> the earlier one the compareto method incomparable was taking

29635.788 -> just one parameter here.

29637.216 -> It is chicken two parameters, right?

29639.3 -> And what you could do is you could simply compare

29642.992 -> based on name right

29644.6 -> since name is a string you could do S1 dot name dot

29647.871 -> compared to S 2 dot name.

29649.5 -> This would compare based on name.

29651.4 -> There's another one you could have one more class created

29654.588 -> which is nothing

29655.5 -> but rule number comparator which implements again comparator.

29660.3 -> Now here you would use the same logic

29662.668 -> that you defined earlier for rule number.

29665.3 -> All right.

29665.919 -> If S1 dot roll number is equal to equal to S

29668.637 -> 2 dot roll number return 0 else

29670.687 -> if S1 dot roll number is greater than x

29673.2 -> 2 dot roll number written one or else

29675.627 -> if it is less

29676.554 -> if S1 dot roll number is less than S2.

29679.081 -> Total number written minus 1 So

29681.2 -> based on this logic you would see

29683.209 -> that the compare or you would see the Sorting Happening

29686.6 -> Now, how do we use this?

29687.911 -> So we have defined a class.

29689.5 -> We have defined a model class.

29691.4 -> So model class is nothing but a class

29693.691 -> that has got just the state right student.

29696.3 -> If you see student doesn't have any Behavior

29698.711 -> as such it doesn't have any method with them.

29701.3 -> It is just a state.

29702.9 -> So this is a model class.

29704.483 -> Alright, so student is a model class

29706.7 -> which has record roll number and name and we have

29709.5 -> two separate comparators defined here named comparator,

29712.2 -> which is comparing the name and we have

29714.009 -> a rule number comparator,

29715.2 -> which is comparing based on rule number.

29718.1 -> Alright now, how do we use it?

29720.8 -> This is not sorting at yet.

29722.436 -> Right?

29722.8 -> How do we use it?

29724.8 -> So how do you use it is

29726.915 -> nothing but you have collections dot sort.

29730.3 -> All right.

29730.943 -> This is pretty much similar

29732.767 -> to proceed other part of the program.

29735.2 -> This is just about putting the data into your class.

29738.7 -> All right, so you have 1 0 1

29740.853 -> put in as Vijay 106 put in as a J1 05 put in as Jay.

29745.4 -> Alright, and now we are trying to sort this

29749.1 -> based on rule number as well as name.

29752.2 -> So both this can't happen in one go by the way.

29755.157 -> All right.

29755.8 -> This is like first you can have something done on rule number

29760.195 -> and so it's not in one go.

29762.1 -> All right, you could do it in step five manner.

29764.9 -> So as you could see here,

29766.55 -> how are we using this comparator

29768.596 -> is nothing but you have collections dot sort

29771.3 -> and then comes the collection

29773 -> that you want to sort.

29774.2 -> In this case.

29775.3 -> It is a L2.

29776.6 -> All right, and then you provide the comparator.

29779.919 -> So here you are providing new name comparator.

29783.1 -> Alright, so after This particular statement

29786.2 -> is called you would see

29787.673 -> that the collection is been sorted based on name.

29790.869 -> All right, and the first one here

29793.171 -> as you could see collections dot saute L2

29795.8 -> and here you are passing roll number comparator

29798.8 -> in the first statement

29800.302 -> or here the first collections dot sort statement would sort

29804.384 -> based on Roll number.

29805.831 -> Whereas the lower one would sort based on name.

29809 -> All right.

29809.8 -> So this is basically offloading

29811.9 -> or just decoupling your comparison logic

29815.1 -> out of your class.

29816 -> That's when you would go with comparator.

29818 -> Whereas you would go with comparable when you

29820.2 -> want to put the logic within the class itself.

29822.805 -> All right, so it depends on what use case you want to do.

29826.3 -> But as far as the performance is concerned,

29828.8 -> it's pretty much the same.

29830.449 -> All right, even

29831.4 -> if use comparable or comparator, it's pretty much the same.

29834.8 -> It just depends on how you want to write

29837.4 -> it the programmers wish so few people refer

29840.6 -> to have modular programming rather than coupling everything

29844 -> into one class.

29844.9 -> They would go with comparator

29846.833 -> and few people like to add things to the class itself,

29850.366 -> which they would go with comparable.

29854.1 -> So what is comparator

29855.3 -> and comparable comparator provide single sorting sequence?

29858.4 -> That is we can sort the collection on the basis

29860.7 -> of single statement such as ID or name

29863.7 -> as we saw that you would have just one compareto method

29867 -> and based on that.

29868.1 -> You would have the sequencing done

29869.9 -> or the Sorting done.

29871.1 -> Whereas comparator you could have multiple learning

29874.17 -> since you could have multiple classes

29876.287 -> implementing this comparator

29877.9 -> and you could write your own logic

29879.7 -> like in the previous example,

29881.29 -> we saw that we had a comparator based on rule number

29884.087 -> and we had a comparator based on name as well

29886.8 -> comparable effects original

29888.592 -> class comparator does not affect the original class.

29891.878 -> So we saw the student class right the student class

29895.1 -> within the student class itself.

29896.982 -> You define the compareto method when you use comparable,

29899.972 -> whereas when you use comparator you wrote different classes.

29903.442 -> So that's about decoupling

29905 -> that I mention comparable provides compare to method

29908.735 -> to sort the elements

29910.2 -> and comparator provides compare method to sort.

29914.6 -> All right comparable is found in Java dot Lang package

29919.069 -> and comparator is found in Java dot util package.

29923.1 -> We can sort the list of comparable type

29926.2 -> by collections dot sort lists

29928.8 -> and we can sort list of elements of comparator type

29932.1 -> by collections dot sort lists comma comparator method.

29936.384 -> All right,

29937.203 -> when I say list, it's a list of some type, right?

29941.1 -> So in the previous case, it was list of student

29944.24 -> and since student class itself at the logic for comparison.

29948.217 -> We don't have to mention it explicitly taken

29951.092 -> care of by itself.

29952.306 -> Whereas in this case,

29953.668 -> where an you use comparator and you had different classes

29957.383 -> where in you put the comparison logic in that case,

29960.7 -> you have to explicitly give the comparator right?

29963.9 -> Like we give something for rule number.

29966.483 -> We instantiated rule number comparator

29969 -> and gave it for sorting

29970.661 -> by a rule number and we instantiated name compare.

29974.2 -> There for sorting by name.

29977.088 -> Alright, so that's how we sort user defined classes.

29981.4 -> So basically why do we have comparable and comparator just

29985.6 -> to reiterate but jvm or Java wouldn't know

29989.566 -> how to sort a user-defined class, right?

29992.6 -> It could be based on rule number.

29994.482 -> It could be based on names.

29996 -> It won't know by itself what you're trying to do.

29999 -> So that's how you using.

30000.7 -> This interfaces you express your logic of comparison.

30006.5 -> So what is XML so Henry handles the database of a college

30011.4 -> but the data is stored in a form of XML file.

30014.7 -> He wants to extract information from this now.

30018.2 -> He is learning XML so that he can handle it easily.

30022.6 -> So what is XML all about?

30024.646 -> It's extensible markup language.

30027.265 -> It is designed to store

30029.1 -> and transport data XML has hierarchical human

30033.3 -> readable format XML is platform independent

30036.6 -> and language independent.

30038.5 -> Why did XML come into picture at the first place?

30041.7 -> So it's basically you have different systems Mauro

30044.9 -> you might develop some system or you might have some service

30048.4 -> that is exposed to the outside world.

30050.9 -> So what happens is they has to be some contract you as a client

30055.192 -> or you as a service provider.

30057.2 -> First of all would expose a contract saying

30059.9 -> that if you give input to my service in so-and-so format,

30063.5 -> I will give you output in Swann Format,

30066.075 -> so basically when you want to send data from a client

30069.6 -> the service you would send it in a specific format

30073.01 -> that the client understands or the server understands.

30076.8 -> So the server exposes

30078.6 -> or the server expresses the input format

30081.6 -> in a XML form and this is platform independent.

30085.3 -> This is like you might have a service tomorrow

30088.1 -> in created in.net which can use the same XML

30091 -> as used by Java program as well.

30093.117 -> So it's a platform independent thing.

30095.5 -> Basically, it's used for carrying data

30097.7 -> as I said store and transport of data,

30099.961 -> which we'll see in the coming slides

30102.1 -> but you could imagine this as nothing but a file

30105.6 -> which is used to send data from your client

30108.07 -> to the server for communication.

30109.9 -> It's pretty much human readable.

30111.5 -> It's not like yesterday we saw

30113.087 -> but serializing and serializing the state of the object

30116.348 -> which was not human readable.

30118.1 -> So this one is pretty much human readable you could imagine

30122.179 -> like you would have an employee ID

30124.5 -> or You want to start something in the employee directory

30127.529 -> and there's a service

30128.691 -> which is exposed for that you could imagine

30130.917 -> that you could send the ID to it

30132.892 -> or you could send an employee name to it

30135.3 -> and format in which it is sent

30137.192 -> would be pretty much human readable.

30139.4 -> You could see that okay, there's an ID

30141.4 -> there is a name

30142.216 -> which is sent to the server and the server is doing so

30145.1 -> and so things so it's hierarchical

30147.952 -> and it's pretty much human readable again,

30151 -> as I mentioned platform independent

30153 -> and language-independent.

30154.64 -> It's agnostic of all these Technologies.

30157.2 -> So there are a lot of existing Services

30159.978 -> which use xml's as a part of input data and output data.

30164 -> So as we go through the examples,

30166.5 -> you should be clear to you guys about what XML is all

30170.5 -> about why we need XML XML is an industry standard

30175.053 -> for delivering content on the internet.

30178.076 -> So it's a standard.

30179.6 -> So most of the services most of data entry communication

30183.4 -> that's happening within in Annette is done

30186.133 -> in the form of XML.

30187.434 -> They communicate with each other in the form of XML XML

30191.2 -> is designed to store

30192.7 -> and transport data XML is the extensible

30195.9 -> because it provides a facility to Define new tags.

30200.2 -> It's not that once you define it.

30202.3 -> It's all done.

30203.4 -> So it's extensible.

30205 -> It's extensibility feature wherein I can say today,

30208.437 -> my server is accepting employee ID and employee named tomorrow.

30212.745 -> My server want to accept employee salary as well.

30216.178 -> So you could add that to it add tags to it,

30219.094 -> which makes it extensible.

30220.853 -> So it's not one time Define.

30222.817 -> You could change it.

30224.228 -> You could evolve the xml's XML is used to describe the content

30228.516 -> and structure of data in a document.

30230.921 -> So it has got its own schema and you can say

30233.811 -> that my XML is going to contain just email ID

30236.7 -> and employee named nothing else and you could validate VL XML

30240.9 -> or the actual XML

30241.906 -> that you have against the schema

30243.8 -> and if you Some extra parameters put in it.

30246.495 -> Would throw you an error.

30248.1 -> So that's about white need XML.

30250.8 -> Let's talk about what are the features of XML?

30254.5 -> Why is it so widely used writing XML is pretty much easy.

30259.4 -> As I said,

30260.058 -> it's human readable and you could actually write it

30263.2 -> and there's a lot of API or lot of sdks

30266 -> that are exposed for reading

30267.965 -> and writing with xml's and very optimized version of it.

30271.868 -> So you could see parses, right?

30273.952 -> We had multiple parses.

30275.5 -> It's for Performance Based on the needs

30278.095 -> of your particular application

30279.902 -> or the nature of your application.

30281.891 -> You would select one of the parsers.

30284.1 -> So writing xml's is very easy.

30287.1 -> The other one is XML data can be extended with DTD and xsd.

30292 -> It's a schema description.

30293.8 -> As I said, you could extend it.

30295.737 -> It's not that it's one time Define.

30297.85 -> You could extend it XML

30299.305 -> can work on any platform this platform agnostic.

30302.378 -> You could run it on any platform either Dot.

30305.037 -> Or it could be different languages or different platform.

30308.5 -> It could be different operating systems as well.

30311.296 -> I could run it on line X tomorrow

30313.2 -> or I could run it on dotnet any tool can open XML file

30317.907 -> and can parse it in programming language.

30320.96 -> So simple editor or even notepad you could open it

30324.7 -> in notepad plus plus and just you through it

30327.6 -> and there are different tools available in the market as well,

30331.2 -> which would give you kind of format your xml's

30334.18 -> so that it's much more readable.

30336.3 -> So there are a lot of tools available already

30339.2 -> XML separates data from HTML.

30342.7 -> It separates the actual data

30344.4 -> from HTML code XML simplifies data sharing.

30348.5 -> So basically as I said it

30350.6 -> pretty much intercommunication standard between systems,

30354 -> you just have to put it into XML

30356 -> and you share it across systems XML simplifies data transport.

30360.978 -> What is the difference between XML and HTML

30364.5 -> so XML is used for storing data and data communication.

30369.242 -> So as I said inter system communication standard

30373 -> and HTML is used for display.

30376.1 -> So whatever you see on the web is something

30378.9 -> that is you have a HTML page you have coded it in HTML format

30383.6 -> and it's used for displaying it XML uses user-defined tax HTML

30390.115 -> has its own predefined tags.

30392.4 -> So when you define your XML, it's a user-defined XML.

30396.2 -> As I said today.

30397.156 -> I might have a service

30398.47 -> which is taking employee ID and employee name

30401.1 -> which is like user defined which is not predefined.

30403.8 -> Whereas when you use HTML HTML is nothing

30407.1 -> but it has to get parsed

30408.95 -> into or it has to get past into a page

30411.8 -> which has been visualized by clients.

30414.4 -> So that's why you have a predefined tags.

30417.212 -> You cannot have anything you

30419.181 -> cannot put something of your own or if you put your own tags,

30423.4 -> it would show up an error.

30425 -> So it's validated reason being you have to compile it

30428.502 -> or you have to run through to show it as a view

30431.6 -> or show it as a HTML page with the plants.

30434.7 -> There's an interpreter

30435.8 -> which has to understand what you're trying to do.

30438.1 -> So it's predefined

30439.4 -> tags XML is case sensitive and HTML is case insensitive in XML.

30445.684 -> It is mandatory to close all the tags.

30448.6 -> So you cannot keep any tags open.

30451.2 -> So we'll talk about the tags.

30453.3 -> Once you see the format of the xml's but basically

30456.3 -> if you have a every property or every data

30459.3 -> that you want to send out will be enclosed

30461.8 -> in a tag you'll have to ensure the tag is closed.

30465 -> So for example employee ID right employee ID will have

30468.8 -> opening tag and it will have an employee ID as a value

30472.5 -> and you will have to close the tag you have to ensure

30475.6 -> that employee ID tag is closed right after the value in HTML.

30479.369 -> It's not mandatory

30480.5 -> to close the tax all the time XML is dynamic

30483.62 -> because it is used to Transport data HTML is static

30487.249 -> because it is to display it it.

30489.5 -> So basically when I say, it's Dynamic it's extensible.

30493.4 -> So tomorrow you could change it.

30495.6 -> You could change the format

30497.3 -> or you could change add few more elements

30500.4 -> or few more tags or add some attributes.

30503.8 -> So it's pretty Dynamic would change it

30506.3 -> whereas HTML is aligned to a proper predefined tags

30510.6 -> and you can't change return.

30512.647 -> You cannot add some tags additional tags

30515.5 -> of your own XML preserves

30517.489 -> white space and HTML does not preserve white space.

30521.7 -> So what are the rules let's talk

30524 -> about XML rule XML considers white space as the actual data.

30528.9 -> So whatever you are sending data through XML.

30532.2 -> So imagine you are sending data between two systems, right?

30536.419 -> So space is also a character when it comes to XML.

30539.9 -> So suppose you want to send some data

30542 -> that is client is typing.

30543.866 -> So of course you need To have Space Center as well.

30547.558 -> You cannot have spacing node.

30549.7 -> It's actual data between two systems communication

30552.8 -> between two systems and since space is valid data.

30556.547 -> It's been considered as data by XML ordering

30559.806 -> and nesting of XML document should be proper.

30563.1 -> As I said,

30563.73 -> you have to ensure that once you open

30566 -> a tag you have to close it there could be nesting

30569.2 -> so there could be a tag

30571.1 -> with says employ and within employed tag,

30574.216 -> you might have employee ID tag,

30576.4 -> and you might have employee name tag.

30578.536 -> And once you have this employee ID

30580.477 -> and employee name tag,

30581.828 -> you have to ensure that you close the employee tag.

30584.9 -> So that's nesting.

30586.146 -> So your nesting ID and name within employee tag.

30589.4 -> So your this might be really confusing at this point.

30592.051 -> If you have no idea

30593.023 -> about what the structure of XML is all about,

30595.611 -> but don't worry in the coming slides.

30597.8 -> We have examples

30598.9 -> and it's pretty straightforward XML tags are case sensitive

30603.186 -> every opening tag must.

30604.806 -> Have a close tag else XML be not correctly function.

30608.4 -> What does an XML file consists of it has one root element

30612.707 -> that is one tag,

30613.988 -> which encloses the remaining tags.

30616.7 -> So it has one root element

30618.7 -> within which the entire content would be

30621.8 -> and each elements consist of start tag content tag

30625.6 -> and an end tag.

30627.2 -> So there is one of the components

30629.5 -> of XML is nothing but element

30631.7 -> within an element you would again have

30634.4 -> some content expressed in form of element again,

30637.832 -> which will have start tag content tag again

30640.84 -> and end tag.

30641.7 -> This is about nesting it will see in the example

30645.013 -> which is pretty much like readable format XML tracks

30648.5 -> are case-sensitive opening

30650.6 -> and closing tags should be

30652.7 -> exactly the same without any difference in the case.

30656.3 -> So you have to ensure

30657.7 -> that it's been enclosed with the same case

30660.433 -> as it was started off.

30661.9 -> This is an XML.

30663.392 -> So the first That you see is nothing but XML declaration.

30667.7 -> The first line that you see here rather is nothing

30671.1 -> but XML Declaration of prologue.

30673.5 -> So this is nothing but kind of saying what the XML is

30677.366 -> or the format in which it is encoded here.

30680.4 -> You could have your dtds

30682.067 -> which we'll see in the coming slides

30684.5 -> but so kind of summarizing your XML what the XML is all about.

30688.8 -> That's your Declaration of prologue and that's mandatory.

30692.3 -> If you don't put it it would throw you an error then

30695.3 -> comes the student tag,

30696.665 -> which is user defined you

30698.293 -> could imagine this as a user-defined XML,

30700.838 -> right and you could imagine this as data being

30703.7 -> or you could have a service a for example,

30706.1 -> which is doing something with this data may be inserting

30709.1 -> to a database right?

30710.446 -> So you could imagine this being sent from client

30713.535 -> or you have a webpage say for example,

30716.067 -> wherein you enter first name last name

30718.8 -> and email address of a student and say for example

30722.178 -> that comes to a server and it's loaded.

30724.8 -> To your database.

30726.1 -> So the root element

30727.479 -> of the document is nothing but student here,

30730.6 -> you can see a student tag.

30732.4 -> And as you can see here,

30734.037 -> it's an element

30735.061 -> which starts with angular bracket then the name

30738 -> of the element and it ends with the angular bracket.

30741 -> So this is student and then the next line is

30744.3 -> about you define three tags within it.

30747.1 -> This is nothing but the content of student

30749.256 -> and here you can see it's following same strategy

30752.104 -> or it is following the same structure.

30754.317 -> You have was named Henry

30756.2 -> and disclosed the first name element.

30759.1 -> You can see the second element as last name and with starts

30762.784 -> with angular bracket last name and and the angular brackets.

30766.545 -> Then there is actual value lie,

30768.578 -> and you could see that it ends with the tag

30771.332 -> or with the element last name.

30773.3 -> So one thing to remember here is about start and ending

30777.5 -> of a tag ending of element.

30779.8 -> You can see the right after the value.

30782.1 -> The element is closed and you can see This thing here as well.

30786.2 -> So student is a element

30788.5 -> and you can see first name last name

30790.999 -> and email being nested into student element nested

30794.5 -> or they are the child elements of the root element.

30797.5 -> So you have child elements defined here

30800.7 -> and you have the last line

30802 -> which defines the end of the root element here.

30804.991 -> We have XML which has doors or which is used to transport.

30808.78 -> First name last name

30810.109 -> and email address of a student across systems.

30813.2 -> Let me show you the tree structure of this XML

30816.391 -> so it could be imagined as student being the root element

30820.45 -> and you can see that first name last name

30823.4 -> and email is nothing

30825 -> but your child or is the child for student

30828.7 -> since it's a root element and you could see the values

30832.1 -> the actual content of it within your first name tag,

30835.463 -> you saw the value Henry within the last name

30838.3 -> you saw the value lie

30839.874 -> and within the email address you saw Henry 123 at gmail.com.

30844.7 -> So the leaf node is nothing but the content of elements

30848.5 -> or the actual contents of the XML

30850.516 -> that you're trying to send across systems.

30853.1 -> This is pretty straightforward.

30855 -> Like you could realize XML in a form of free format

30858.1 -> where in your root node is nothing but element of your XML

30862.5 -> and the leaf nodes

30864 -> or the leaves are nothing

30865.904 -> but the actual value stored in the XML.

30868.9 -> So let me talk about three rules in this given example student is

30874.7 -> a root element.

30875.946 -> Then first name

30877.1 -> last name and email are descendants of student.

30880.7 -> This is pretty much straightforward

30882.4 -> when it comes to tree

30883.848 -> so you have a root node and you have descendants

30887.091 -> and we can see from the structure

30889.5 -> and sisters in this example student is ancestor

30893.5 -> of all other elements,

30895.6 -> so root node,

30896.709 -> so it's ancestor

30898 -> of all other elements within this tree order

30901.307 -> XML attributes you can have attributes.

30904.5 -> Which are common across

30906.4 -> or you could have some attributes defined

30909 -> within an element.

30910.295 -> So here we can see that message.

30912.6 -> That's nothing but an XML with the root node messages

30916.3 -> and you could see individual messages within so

30920.1 -> there are two messages here within messages Tab.

30923.6 -> And the first one is to any and it's from John

30927.9 -> and you have a body there the actual body of the message

30931.4 -> what you want to send and you can see here this ID

30935.189 -> or this something

30936.4 -> that has been provided as an attribute,

30938.821 -> which is nothing but you could see Mi di is equal to 1

30942.2 -> that's attribute has to be enclosed within single quotes

30946.248 -> or double quotes.

30947.5 -> So whatever you see within the element

30950.379 -> and closed within codes

30952.173 -> that is nothing but attribute so modifier,

30955.327 -> you can say some kind of a modifier to your element.

30959.5 -> So attributes add more information about the element

30963.2 -> it is adding some more Formation

30965.4 -> to the element XML attributes must always be coated either.

30969.6 -> It should be within single quote

30971.74 -> or you could have it within double quotes here.

30974.819 -> We have it within double quotes for our XML comments.

30978.6 -> So to make it more readable

30980.605 -> or to increase the maintainability of an XML

30983.7 -> so that someone else can understand

30985.839 -> what you are trying to do you could have comments put in

30989.3 -> so this is pretty much similar to comments in other languages.

30993.2 -> The reason why we rationale behind why we put the comments

30997 -> it's more about make it much more verbose

30999.637 -> and understand what bag is all about how we comment

31003.038 -> is nothing but you have opening angle bracket.

31006.1 -> Then you have exclamation mark then two hyphens and after the -

31010.58 -> you have the comment and

31012.3 -> once you have the comment you close it with double -

31015.8 -> and then closing angle bracket.

31017.9 -> So one thing to note here is exclamation mark,

31020.769 -> is there only when you start the comment

31023.2 -> and at the end you don't have Exclamation mark double -

31026.619 -> and then closing angle bracket similar comments are just

31030.1 -> like HTML comments comments are used to make

31033.086 -> the code more understandable.

31035.148 -> What are the rules?

31036.449 -> Do not Nest a comment inside the other comment?

31039.606 -> Okay, you can't Nest it.

31041.353 -> And I don't see any need

31043.095 -> to nested was your just expressing it

31045.7 -> or we are just adding comments to make it more readable.

31049.5 -> So if you nested it would give you an error do not use comments

31053.423 -> before and XML declaration XML declaration should be

31056.696 -> the first line.

31057.6 -> You shouldn't be using comment before that comments can be used

31061.3 -> anywhere in XML file except attribute value.

31064.4 -> So you can't put comment within an element

31067.038 -> or you can't put it right

31068.686 -> after the element is defined or say,

31070.898 -> for example, you have this message tag,

31073.3 -> right which starts with angular bracket and then message

31076.352 -> and right after the message.

31078 -> You can't have comment your element tag has to be closed

31081.8 -> after this closing angular bracket you could Any comment

31085.283 -> but it cannot be

31086.247 -> within this space wherein you define the attribute

31089.2 -> so basically comment can be put anywhere

31091.5 -> but it cannot be as attribute value.

31094.045 -> So let's see a well-formed XML

31096.3 -> and what do we call well-formed XML

31098.9 -> as there must be exactly 1 root element and XML

31103.53 -> should have exactly one root element.

31106.3 -> You cannot have multiple every start tag has a match intact.

31111 -> So we saw in the previous example,

31113.03 -> like if you start student you have to ensure have an intact

31116.6 -> for student as well.

31118 -> So that's what it is about every start tag must have

31121.783 -> an end tag attribute must be coated either with single quotes

31126.025 -> or you could have double quotes comments

31128.698 -> and processing instructions may not appear inside a tag

31132.536 -> cannot be inside a tag

31134.1 -> and you have opening angular brackets or

31137.4 -> and must not occur inside a data element.

31140.7 -> Your data cannot have this as value or your data element

31144.195 -> cannot Contain this as a part of the name of element.

31147.5 -> So let's move towards XML validation.

31150.8 -> So well-formed XML can be validated

31153.7 -> against DTD or xsd.

31156.5 -> So communication between multiple systems you have

31160 -> to ensure plant is sending data or is kind of you know,

31164.159 -> preparing an XML

31165.391 -> which is aligned to what server expects right?

31168.819 -> So that's where you have decreed in the and xsd.

31172.4 -> Let's see.

31173.2 -> What is D TD.

31174.8 -> E TD is a EB NF grammar defining XML structure.

31179.4 -> It's a normalized form at grammar,

31181.7 -> which defined XML structure a DTD defines a legal element

31187.5 -> of an XML document.

31189.022 -> So it says what XML can contain what an element could be

31193.5 -> or what the attributes could be and it's a legal element.

31198.1 -> Okay.

31198.452 -> So basically when you define

31200.449 -> a DTD you can expose the service today,

31203.132 -> which could be used by Tomorrow right?

31205.745 -> Google can be using it for some purpose.

31208.5 -> So this is a legal document saying that my service expect

31213.4 -> or accepts the times 1 so format,

31216 -> so you have to send it in so-and-so format

31218.46 -> for us to process it through.

31220.3 -> All right.

31221 -> So it's a legal document between multiple organizations

31225 -> XS T is nothing but used to address the shortcomings

31229.4 -> of DTD uses name space to allow for reuse

31233.7 -> of existing definitions.

31235.46 -> So you could Define an xsd and you could just use it

31239.2 -> or through name spacing you can have it within other pieces

31243.631 -> of xml's as well.

31244.939 -> So, let's see.

31246.016 -> What is GT D PT d stands for document type definition.

31251.43 -> DTD is used to define structure of an XML document

31255.2 -> or DTD defines the legal elements of an XML document

31259.8 -> as we spoke.

31260.8 -> It defines legal elements,

31262.9 -> or which cannot be Accepted so

31265.3 -> basically you define what your XML is all about through DTD

31269.1 -> so you could see a student DTD here.

31271.9 -> So you have XML

31273.1 -> which is nothing but which has student

31275.551 -> which has first name last name email and marks.

31278.6 -> All right.

31279.4 -> This is what you have within your XML.

31281.7 -> Now you define a DTD

31283.3 -> which could be put into your doctype.

31286.019 -> So the first tag

31287.229 -> that you see is nothing but declaration

31290.084 -> and it's linking your kind of tying it against a DTD

31293.894 -> with that's defined external DTD file.

31296.74 -> All right, you define this

31298.74 -> and you have a DTD file below which is student dot DT D.

31303.1 -> And here you can see that it says

31305.561 -> that within student element you can have

31308.561 -> for other elements or as a nesting of for other elements,

31313.1 -> which is first name last name email and marks.

31317.9 -> All right, if you

31319.83 -> since this DTD is linked with your document or with your ex.

31324.5 -> Mel document now

31325.8 -> if we try to add something if you have one more element

31329.874 -> here which could be like a dress right?

31332.6 -> If you have one more element here,

31334.541 -> which is address.

31335.628 -> It would throw you an error because your ETD says

31338.8 -> that student can have only first name last name email

31342 -> and marks address is not a valid element within student.

31346.3 -> All right.

31347 -> First name now, let's define.

31348.981 -> What can we have in first name?

31350.805 -> Alright.

31351.605 -> So first name is nothing but character data again.

31354.7 -> Last name is a character data email is again a string

31358.3 -> and Marx is again taken as character sort of so this is

31362.8 -> how we Define DTD.

31364.8 -> Alright, so we are trying to establish the structure

31368.59 -> or we are trying to say

31370.25 -> that student can have a nice one so fields

31373.408 -> and if there's something else then it's invalid.

31376.8 -> So here we can see ETD contains root element

31381.5 -> and declare the child elements we can see

31384.4 -> That it says student can have only first name last name

31388.048 -> and email and marks.

31389.6 -> It defines last name child element

31392.597 -> and data from this element is possible right

31396.338 -> when it is PC data.

31397.8 -> It's possible again you have first name,

31401 -> which is possible you have last name,

31403.117 -> which is possible you have email address

31405.341 -> which is possible and you have marks

31407.4 -> which is possible.

31408.6 -> All right.

31409.1 -> So what is XML schema XML schema is used to express constraints

31414.2 -> about XML document.

31416.4 -> All right, it's pretty much it does the same purpose as DTD

31420.4 -> but it's much more advanced than DTV.

31423.2 -> It has much more features XML provides more control

31428 -> on XML structure

31430 -> a well-formed XML document can be validated against xsd.

31435.7 -> So you have an xsd again similar to DT

31438.7 -> which defines the structure

31440.6 -> and a well-formed XML should be validated

31443.6 -> or should be Against a particular axis T.

31447 -> So here we see an xsd,

31449.3 -> which is much more verbose

31451.3 -> or which is much more clearer

31453.53 -> to understand compared to DT DT D was something

31457.384 -> like was not expressing to that extent

31460.3 -> but X is T is pretty clear

31462.484 -> in terms of what the content could be.

31465.6 -> Again.

31466.4 -> It defines the root node and declare the child elements.

31470.7 -> So here you can see

31472.073 -> that exists is defined in a form of XML itself.

31475.4 -> All right, it follows the same pattern as the XML.

31478.9 -> So it says element which is a keyword.

31481.6 -> All right element is a keyword for your xsd

31485.1 -> and you have student as a attribute.

31488.3 -> So this you could realize xsd as I said as an XML itself,

31493.2 -> it's a valid XML cracker,

31495.113 -> which says that you have an element with name student now

31499.377 -> what can students hold is again a sequence

31502.5 -> when you say sequence it has to The same sequence break

31506.156 -> the sequence it's again going to be invalid

31509 -> then it says first element

31510.8 -> first child element within student should be first name.

31514.6 -> The next one to follow should be last name.

31517.3 -> The next one should be email

31519.353 -> and the last one should be marks.

31521.7 -> All right, and it defines what type is

31524.5 -> particular elements hold.

31526.7 -> So first name is a string.

31528.7 -> Last name is a string.

31530.392 -> You may raise a string and Marx is a string as well.

31534.4 -> So this is how it is you define a structure to the XML

31538.3 -> and you have to ensure for your XML to be valid.

31542.6 -> It has to be valid

31543.932 -> against this exists e it's a similar scheme are descriptive.

31548.6 -> So what's the difference between DTD and Xs T DT

31552.5 -> v stands for document type definition XS d stands

31557.4 -> for XML schema definition.

31559.9 -> DTD is not extensible access T is X Zebra dpv

31566 -> provides less control

31567.7 -> on XML structure xsd provides more control on XML structure.

31573.2 -> ETD does not support data types xsd supports data type.

31578.8 -> We sort the data types like string and stuff which is

31581.883 -> like it supported just in exist.

31583.885 -> You don't have DTD supporting

31585.7 -> and DTD does not define the order of child elements

31590.5 -> as we could see it just says

31592.089 -> that you could have four elements within but it

31594.7 -> doesn't have any specific order as such whereas

31597.78 -> when it comes to xsd.

31599.187 -> You could Define a sequence right as we saw

31602 -> in the previous example,

31603.2 -> we said that the first one should be the first name,

31605.8 -> then the last name then email ID and then marks

31608.9 -> so you could Define the sequence

31610.5 -> in which your sub elements should occur XML CSS file CSS

31615.8 -> is used to add more tiles to the XML document.

31620.2 -> So if you want to color coded or do something that's

31624.1 -> when You CSS pretty much similar to HTML document.

31627.775 -> So here we can see that you could Define student

31631.3 -> which has got a background color of pink.

31634.3 -> Then you have first name,

31636 -> which has different font sizes here.

31638.333 -> First name last name and email ID and marks

31641.133 -> which has got different font sizes.

31643.8 -> So we want to have font size of 25 for this child elements.

31649.2 -> You want to display it as a block and color

31652.5 -> as white and the margin left as 50 pixels.

31656.8 -> All right,

31657.9 -> when you have such thing defined if you want to link it up

31661.6 -> if you want to link CSS to XML,

31665 -> you need to have a XML stylesheet tag defined

31669.1 -> and you would type as text or css

31673.8 -> and you put H ref as

31675.6 -> your CSS name to make the changes in the styles

31679.113 -> of the XML file CSS file is linked to XML file

31682.545 -> through this statement.

31684.3 -> So this is how you link your CSS file to your XML file.

31688.8 -> Now.

31689.4 -> What is XS L XS L stands

31692.2 -> for extensible stylesheet language XSL navigates

31697 -> all the nodes

31698.146 -> and elements and display XML data in a particular format.

31702.5 -> All right, it's basically

31704.07 -> for parsing sort of it navigates through all the nodes

31707.4 -> and elements queries can be specified in XSL.

31710.9 -> If you want to query some particular data

31713.4 -> or like we had message this thing in a couple

31716.457 -> of slides back.

31717.5 -> We saw multiple messages within message, right?

31720.7 -> So if you want to read some messages extract the messages

31724.5 -> that are sent by the users

31726.4 -> you could wear it out using excessive it displays data

31730.325 -> on the browser as

31731.585 -> per the format given in the Excel file.

31734.742 -> So, let's see what is accessible file all about.

31738.6 -> Okay.

31738.924 -> So here what you're doing is nothing

31741.2 -> but you're extracting data.

31743.1 -> All right, you are.

31744.383 -> Acting first name.

31745.6 -> So the first name here would be taken from your student

31749.224 -> and would be displayed here.

31751 -> And again the second one

31752.799 -> you have last name you select the last name particularly.

31757 -> This is acting upon student dot XML.

31759.851 -> All right, how do you

31761.467 -> link up accessible to XML is pretty much similar to CSS.

31766.1 -> You have style sheet and you have type as text /

31770.1 -> XSL and not CSS,

31772.4 -> right and you have H ref as student accessor.

31777.7 -> So that's 4X s l-- and again, let's see.

31781.5 -> What's the difference between CSS

31783.5 -> and Xs L fi CSS files are easy to understand

31787.8 -> Excel files are difficult to understand CSS is less powerful

31792.338 -> than accessible CSS is specifically for display right

31796.9 -> changing the font size changing the colors background colors

31800.6 -> and foreground color and everything XSL is more.

31804.258 -> Full then CSS

31805.3 -> since you can extract data or do something with it.

31808.633 -> Basically, it's a processor.

31810.5 -> You actually can process the XML using Excel CSS

31815.1 -> does not use XML notations Excel uses XML notations,

31820.146 -> which helps in writing code.

31822.4 -> CSS can be read by modern web browsers XSL

31826.451 -> is not supported by many web browsers.

31829.8 -> Now, let's talk about XML parsers.

31832.9 -> Okay.

31833.6 -> So XML parser is nothing but you parse through you

31837.2 -> have an XML and you want to read data from it

31840.147 -> or XML parsers could be used for writing the XML as well.

31843.9 -> Okay, creating an XML could create an XML

31847.215 -> using XML parsers as well

31849.207 -> or you could read through the existing xml's.

31852.7 -> So an XML parser is a software Library

31855.546 -> which provides client applications to work

31858.7 -> with XML document and XML parser is used to check

31863.3 -> whether the Comment is in well format or not.

31867.8 -> It is basically used

31868.8 -> for compiling our parsing your XML as well.

31872 -> It is used to validate an XML document

31875.174 -> and parsing XML refers to going

31877.558 -> through XML document to access data

31880.174 -> or to modify data in one or the other way.

31883.4 -> All right, you could actually read through the xml's

31887.292 -> or you could extract data

31889.202 -> or you could modify data using XML parsers.

31892.8 -> What a bar says here.

31894.266 -> You could see XML document right being sent

31897.2 -> to the parser parser is nothing but API

31900.1 -> so you send the XML

31901.8 -> The Source XML or the XML that you are trying to pass

31904.99 -> is going to be sent to the XML parser

31907.2 -> and this API is going

31908.813 -> to be used by client application right to parse the XML files.

31913.7 -> So XML parsing could be broadly classified

31916.853 -> into two different types one is object-based

31920.2 -> and one is event-based right object-based is nothing

31924.365 -> but document object model or it is also known

31927.7 -> as Dom even base.

31929.3 -> We have two different parses

31931.126 -> when it comes to even based one is sacks

31933.669 -> and the other one is tax.

31935.6 -> All right, so let's talk about object based model Dom parser.

31942.3 -> It stands for document object model.

31946.176 -> It is an object-oriented

31948.6 -> representation of an XML parser tree.

31952.5 -> So remember we assign XML

31955 -> and we passed it into a tree like structure

31957.857 -> where in your root node of the tree was the root element

31961.6 -> from your XML

31962.51 -> and we had all the elements

31964.4 -> and at the end the leaves were nothing but the values

31967.949 -> or the data

31968.7 -> that the XML stores actual values right

31971.734 -> or XML stores or care.

31973.8 -> Rather, so that's what trees all about.

31977.4 -> It defines the standard way to access and manipulate

31980.4 -> documents Dom is a common way for traversing the tree.

31984.5 -> So as we look through the examples,

31986.962 -> you should get Fair idea

31988.7 -> about it creating an XML document using Dom parser.

31992.7 -> So what is required to use Dom parsers?

31995.414 -> How do we do that?

31996.8 -> First is you have to import all the parsers.

31999.628 -> You have to import all the classes

32001.8 -> that you have within partial Java x

32004.508 -> dot XML dot parsers.

32007.1 -> These are all input statements that you have.

32009.4 -> You have to import different packages

32011.403 -> which when you use IntelliJ or Eclipse,

32014.9 -> it would prompt you to import

32016.9 -> it it would suggest you to import it.

32019.092 -> So you did not actually write this input statements,

32022.203 -> but it's very important

32023.561 -> to understand what we are trying to do here.

32026.2 -> So these are different packages that we are trying to import

32029.715 -> and as you could see all your XML related classes.

32033.8 -> Are put into Java x

32035.4 -> dot XML dot transform or basically G of x

32039.2 -> dot XML package.

32041.6 -> So once you import it,

32042.989 -> you can start using the classes within the first thing

32046.4 -> that you do is when you generate an XML,

32049 -> you have document Builder Factory,

32051.3 -> so you have document build a factory dot new instance.

32055.022 -> You create a new instance of it

32057.2 -> and you get document build a factory that's instance of it.

32061.9 -> So now with the document Builder Factory instance

32065.6 -> that you got you would create a new document Builder Okay.

32070.035 -> So this is a factory design pattern.

32072.8 -> We have a design pattern in Java

32074.906 -> and document Builder factor is nothing but it's following

32078.466 -> a factory design pattern, right?

32080.5 -> You don't have to think much about it.

32082.676 -> But basically what we are trying to do is instead

32085.5 -> of creating the instance of something on our own which is

32089.3 -> like we usually do with new and the class name, right?

32093.4 -> Sort of doing it on our own Factory design pattern is

32096.697 -> nothing but the creation logic is written within a class

32100.146 -> which is not exposed to you.

32101.945 -> So you need not create it there's some class

32104.696 -> which creates instance for you.

32106.782 -> All right, and that is nothing

32108.8 -> but a factory class then you create a document Builder.

32112.9 -> So it's nothing but F dot new document Builder.

32116.8 -> Okay, you handle exceptions and everything here.

32120.25 -> So now let's start with creating the actual document.

32124.5 -> You have the root element as students.

32128.2 -> All right,

32129.4 -> and within student you have student within students

32133.9 -> you create student

32135.107 -> and within student you have like first name last name email

32139 -> and marks and you could see first name put as Henry.

32143.7 -> So how do you create element is nothing

32146.4 -> but using dog create element,

32148.541 -> how do you create X node or text node

32151.2 -> or the actual value that you have?

32153.562 -> Then your element you would do it with create text node,

32157.8 -> and you could Nest it using appendchild.

32162 -> So basically you have first name appended to T1,

32166.3 -> which is nothing but this one right T1

32169.2 -> is appended to the first name first name element

32172.9 -> that you have T2,

32174.2 -> which is the text node, which is holding.

32176.7 -> The last name is appended

32178.6 -> to the last name element p 3 is appended to email element

32184.1 -> and the for which is your marks

32186.3 -> which is appended to Mark's element.

32188.866 -> So basically this is how you make nesting

32191.8 -> of your nesting within the xml's.

32195 -> Alright.

32195.8 -> So once you create this document you append all the child's

32199.6 -> and everything you create a well-formed document here.

32203.4 -> Are you create an XML here and all the XML

32206.9 -> that you would get is within this dog,

32209.6 -> since we are creating element you could see here we are.

32213.3 -> Getting elements within doc creating elements and text node

32217.128 -> and everything within dog.

32218.8 -> So at the end once you have all this done,

32221.953 -> you would have a well-defined XML stored as a form

32225.799 -> of document class.

32227.2 -> So we want to print this particular document

32230.3 -> in a text format,

32231.433 -> right which could be readable by us

32233.7 -> or do you want an XML out of it?

32236.23 -> So that's when we use Transformer.

32239 -> So there is a transform Factory dot again since it's

32242.5 -> a factory design pattern.

32244.249 -> It's exposing a method

32245.789 -> which is nothing but new instance.

32248.125 -> So you create a new instance of Transformer factory

32251.971 -> and you create a new Transformer.

32254.9 -> So at then what you get is nothing but a Transformer

32258.2 -> and what are we trying to transform is nothing

32261.3 -> but we are trying to transform the object

32264.4 -> or the document object that we created.

32267.7 -> We are trying to transform it into a human-readable text file

32272.1 -> or the XML file all So

32274.1 -> that's a transformation that we are trying to do here.

32277.1 -> So here you could see

32278.637 -> that you transform it TDOT transform

32281.2 -> and you pass the document object

32283.31 -> that you created and put the element into element

32286.621 -> and text notes

32287.587 -> and everything into which is holding a valid XML.

32290.9 -> You are trying to transform it into a XML file.

32294.376 -> So how you do that is T dot transform.

32297.5 -> Then you have the new Dom source

32300.4 -> and you specify the instance of document

32304.5 -> which holds your XML then you have stream result

32309 -> and new stream result class

32311.043 -> which takes file output stream as its parameter.

32314.6 -> So you have to pass the parameter where you

32317 -> want to write this XML to and when you run this at the end,

32320.849 -> we are just printing that XML file is been generated.

32324.4 -> The first thing that we do is we are creating a document

32327.7 -> and using the document.

32329.215 -> We are creating elements the wave that we want.

32332.474 -> So in this case,

32333.474 -> We have a students as the root node

32335.6 -> and within student you have student

32337.707 -> and within student you have first name

32340 -> last name email ID and marks, right?

32342.449 -> We created this structure till here.

32344.9 -> And as you could imagine this is just dealt

32348.13 -> in the form of object.

32349.823 -> Right which is stored in dog.

32352.4 -> So now since you want to write it into a file,

32355.8 -> which is into a human-readable form or which could be

32359.3 -> passed across Network.

32360.9 -> You have to transform this into XML file,

32363.9 -> which could be read.

32365.3 -> So that's what we do here through Transformer.

32368.675 -> We are transforming your document or the XML

32372 -> which is in the form of document into a file.

32375.161 -> So, let's see this program.

32380.4 -> In the meanwhile, we can do one thing.

32383.1 -> I will create one more directory here.

32389.9 -> At Eureka XML.

32393.3 -> Okay, and we don't have any files with them.

32398.9 -> Yeah, let's hold on for a minute.

32401.3 -> Yeah, I just come up.

32402.7 -> All right, so it's the same program that we spoke about.

32406.5 -> So I have loaded into my ID.

32410 -> So we do the same steps here.

32412.007 -> We create all the elements all the required elements and stuff.

32416.4 -> So we are writing it into a file right

32418.576 -> so you could have your own file here,

32420.588 -> whatever file you want to write into.

32424.3 -> okay, so I right into the directory

32427 -> that we created which is nothing

32429.2 -> but Ed Eureka XML we are writing the XML file there.

32436.5 -> All right, let me execute this program.

32447 -> It's building it and

32448.8 -> if it's generated you should get XML file generated at the end.

32456.7 -> So this is about using Dom.

32459.2 -> All right.

32459.946 -> So when you say Dom it's nothing but document object model

32464.434 -> its building it.

32465.826 -> So hold on for a minute.

32468.5 -> In that see I think it should come up soon.

32475.9 -> Right.

32476.313 -> I think it's coming up.

32770.2 -> Alright, so we have this program here,

32772.8 -> which is kind of creating XML document.

32775.8 -> This is same as what we spoke in the slide.

32778.864 -> Right what I walked you through.

32781.3 -> So basically you have students you're creating

32784.181 -> students elements within students element

32787.1 -> you are going to have student

32789.1 -> and then first name last name email and marks.

32792.5 -> Alright, we are going to create a text node

32795.286 -> within this elements.

32796.661 -> So this is nothing but your first name,

32799.149 -> which would go into the first name element.

32801.9 -> This is the last name

32802.802 -> which would go into the last name element

32804.802 -> that we created earlier.

32806.3 -> Then we have email

32807.7 -> and marks going into a prospective element.

32810.8 -> Alright.

32811.6 -> So basically we are nesting it here at the end.

32813.94 -> We have the Transformer

32815.293 -> which is kind of taking the document and converting it

32818.2 -> into XML file that we want.

32820.4 -> So let me go and delete this off and run the program.

32826.4 -> In this folder, we don't have any file right

32829.565 -> I run this program from here.

32838.8 -> So you could see that it says XML file generated.

32843.1 -> All right.

32843.6 -> So let's go to the folder and see up there is a file

32846.6 -> that's generated that is student studying similar.

32849.7 -> Now I can open this

32851.161 -> with any tool say I open it with notepad

32854.4 -> and I see something like this right now.

32857.1 -> I want to format this I want to format this

32859.845 -> into because this is like one single string,

32862.559 -> which is Big right?

32863.843 -> So if I want to format it,

32865.6 -> we have tools that are online,

32867.8 -> even you could format it online, right?

32870.5 -> So I put this and I say I want like three spaces

32874.9 -> or indent level which is good

32877.314 -> and I formatted okay

32878.9 -> when I click the format.

32882.31 -> You can see

32883.11 -> that it formatted the entire XML for me.

32885.6 -> So the basic thing

32887.2 -> that it's doing is just about formatting this XML.

32890.5 -> All right, this is much more readable right after formatting.

32894.049 -> You can see

32894.8 -> that it's readable can see first name as Henry Lee

32897.8 -> and Henry 123 at gmail.com and you have 70 put in here,

32902 -> which is what we expect out.

32903.647 -> Okay.

32904.447 -> So we saw this output after running the program Now quickly.

32908.883 -> Let me run through what's Dom parser

32911.496 -> and how do we use Dom parser for parsing and existing XML?

32915.6 -> All right.

32916.3 -> So these are the classes that you need to import

32918.8 -> which would be suggested by your IDE as well

32921.932 -> either IntelliJ or Eclipse.

32923.9 -> So you have document Builder Factory you use the same thing

32927.9 -> get the new instance from the factory

32930.065 -> where in you get an instance

32931.8 -> of document Builder Factory with this you create document Builder

32935.8 -> and once you have the document Builder you parse it

32939.382 -> Boca parse method

32940.6 -> The document Builder and pass the XML file name, right?

32944.2 -> So whatever XML you want to pass you would send it across now.

32948.144 -> Once you have this past if you want to get the node name

32951.8 -> if you want to display something like what's the root element

32954.9 -> within your XML you could do something

32957.1 -> like this talk dot get document element and get no name.

32961.318 -> So this would basically display the first element

32964.876 -> that you have within your XML,

32967.1 -> which is nothing but the root element right you

32970.083 -> could read this on the name.

32971.9 -> You have the tag names or element name.

32974.8 -> So you have methods

32976.185 -> like get Elements by tag name

32978.3 -> and you could give the name of the element

32981.118 -> and it would retrieve it as a node list.

32983.8 -> Now, you will have to I trait

32985.59 -> through this node list to display the contents of it.

32988.9 -> All right.

32989.4 -> So here what you do is you I trade through it.

32992.047 -> So when you get a node list,

32993.7 -> basically you would get list of notes.

32995.9 -> All right.

32996.533 -> So now what we are doing is we are printing it out one by one.

33000.6 -> Printing the nodes are the contents

33003.2 -> that we have within one by one.

33005.784 -> So in this case,

33007.015 -> you can see that when you do student dot get Elements

33011.046 -> by tag names and you can see student here.

33014.2 -> So this would give the number of student

33016.305 -> that you have within a document the previous example

33019.247 -> that we took the number

33020.6 -> of element is just one right we just had entry for one student.

33024.502 -> So it would I try it.

33025.823 -> Just once in this case it would I try it just once all right.

33029.6 -> And what we are doing here is we are kind of taking

33033.3 -> again element by tag name

33035.4 -> and these are nothing but your actual values

33038.707 -> or the first name last name email

33041.602 -> and marks this Loop is going to run just once

33045.1 -> since we have only one student

33047.112 -> and this is how you display the content of an XML.

33050.7 -> So basically what we are doing is we are parsing it

33053.3 -> when we say parse we are trying to get data

33056.5 -> or we have trying to load data into Dom or document.

33060.9 -> And we are printing it out.

33062.925 -> Why do we have parsers is nothing but to retrieve data

33066.9 -> if you want to query out particular data,

33068.9 -> you could do it.

33070 -> You could write some logic to read out a particular data

33073.9 -> from an XML.

33074.869 -> Say for example,

33076.1 -> you might have a long XML and you want to read data

33080 -> pertaining to student Henry.

33082.6 -> So what you could do here is you could write

33085.353 -> some logic here saying

33086.858 -> that if student is equal

33088.5 -> to Henry then written mock secured by Henry.

33091.7 -> So that's why we have XML parsers in picture

33094.745 -> to have it loaded into memory and play around with it.

33098.5 -> Alright, so let's see

33100.2 -> the example of XML reading using Dom I give the path here

33105.4 -> as see Give the same file.

33110.3 -> All right at Eureka XML.

33113.5 -> Student dot XML

33114.653 -> that we created or let me do one thing.

33126.6 -> So I create one more student here.

33128.8 -> Say for example.

33161.6 -> Just for Simplicity purposes.

33164.8 -> I'm just putting test last name as the last name test email

33170.9 -> and I put test Mouse.

33175.8 -> All right.

33176.388 -> So these are the values

33177.649 -> that I have put for one more student

33179.708 -> that I've created

33180.7 -> or maybe I will put this one as Just to be consistent.

33187.638 -> So we have two students now within so first one is Henry D.

33192.1 -> And the other one is

33193.4 -> like we have created a test to let me show you

33196.357 -> when we run this program.

33198 -> What we are trying to do is we are going to read this XML

33201.3 -> that we have created and it's going to parse

33204.067 -> it parsing is nothing

33205.37 -> but it's going to display the contents of it.

33209 -> So it's going to Loop

33210.235 -> through its going to understand there are two students

33213.1 -> within and it's going to display first name last name email

33217.8 -> and mock secured by each student.

33222.2 -> All right.

33222.9 -> It says the processing instruction.

33231.3 -> Okay, we can see the output being displayed here.

33235 -> All right, so we can see

33236.737 -> two students here the current element and really calm

33240.5 -> and re 1 2 3 gmail.com and 70 and there is one more student

33244.192 -> that we added directly into the XML and we

33246.815 -> can see it displayed as well saying that test first name,

33250.4 -> press last name test email and test marks.

33253.6 -> So that's how we bars it.

33256.2 -> Okay using Dom parser and what Dom parser does is nothing

33260.2 -> but it creates a tree

33261.7 -> if you remember I said it creates a tree like model

33264.8 -> that was there in one of the slides

33266.6 -> that we discussed earlier.

33268 -> It creates a tree-like structure

33270.2 -> with a root element as your root node,

33273.1 -> and your leaves are nothing but this values

33276.1 -> Henry Lee and all this stuff whatever is been displayed here

33280.262 -> or nothing but leaves so of your tree advantages

33283.602 -> and disadvantages of using Dom it is preferred

33286.8 -> when we have to randomly access separate parts

33290.045 -> of the document.

33291.206 -> So if you don't want to do it sequentially its preferred

33295.291 -> that you use Dom it supports both read and write operation.

33299.6 -> So we created XML using Dom

33301.669 -> and we read XML using Dom as well.

33304.2 -> So the first example that we took about creating

33307.3 -> student dot XML was using Dom as well since it was document.

33311.9 -> Remember we created object of document

33314.4 -> and then we inserted all the elements

33316.517 -> within that is nothing

33317.903 -> but Dom it supports both read and write operation

33320.951 -> as we saw and what are the disadvantages of using it.

33324.274 -> It is slower than other parsers since it has to create free.

33328.244 -> So it's a one time activity that it does.

33330.8 -> So remember in the second example

33333.1 -> that we took we saw parse here,

33335.5 -> right the sparse here

33337.2 -> document Builder dot parse this is going to take lot of time

33341.5 -> because it's going to create a tree

33343.6 -> if you XML is big enough based on the size of the XML

33347.235 -> it would take time

33348.493 -> because it's going to create tree.

33351 -> Parsa's something

33352.214 -> that is going to take time and it's not very memory efficient

33356.475 -> since you could imagine if you have a big XML

33359.6 -> so xml's in general are

33361 -> like it could have like a hundred million records

33363.954 -> within they are humongous.

33365.5 -> They are not small examples that we are dealing right now.

33368.609 -> It's coming from different systems, right?

33370.852 -> So you could imagine their system pushing data

33373.5 -> in the form of XML

33374.601 -> and sending it to some other system to process it.

33377.6 -> So it could be humongous could grow up to like

33380.859 -> a hundred million records or something of that sort.

33384.1 -> So imagine that you want to load all this into memory, right?

33388.407 -> I'm create a tree.

33389.7 -> So this parse method is going to take a long time to create

33393.297 -> a tree and the other thing is it's not memory efficient

33396.7 -> because it's going to load this entire document

33399.7 -> into your memory,

33400.9 -> right which is going to take

33402.804 -> like lot of achebe's of memory right to load it.

33406 -> So it's not pretty memory efficient when it comes

33409.1 -> to parsing using Tom.

33411.5 -> So that's the reason we have other variants

33414.1 -> of parsing which is not document object model,

33417 -> which is basically event-based.

33419.446 -> So we have like two parses even base parser one is like

33423.6 -> for push parsing it is sacks

33426.3 -> and whereas for will parsing it is Stacks.

33429.6 -> All right, so we'll just go

33431.4 -> through what is sax parser and sax parser sax parser is nothing

33436.6 -> but it stands for simple API for XML sax parser reads XML file.

33442.9 -> Sequentially.

33444.1 -> It's an event-based right?

33446 -> So when I say even based what happens is

33448.6 -> when a parsing event occurs,

33450.8 -> the parser invoke the corresponding method

33453.392 -> of a corresponding Handler.

33455.1 -> So basically you define a Handler you say

33458.169 -> that if I get so and so tag or

33460.471 -> if I get start of element tag go to this particular Handler.

33464.942 -> All right,

33465.742 -> and this handlers are nothing but user-defined handlers

33469.5 -> so you could say that Not get a start of element tag.

33473.7 -> Go to this Handler and do something, right?

33476.476 -> It could be as simple as

33478 -> printing it or it could be as simple as filtering it.

33481.3 -> So it's up to you to write the logic for the Handler

33484.451 -> but what the framework does is nothing,

33486.8 -> but when you see a opening tag,

33488.866 -> it would give a call to your method.

33491.2 -> Alright you Handler method sax parser is used

33494.8 -> when we have a large XML document.

33498.2 -> As I said in the previous example of you know

33500.982 -> hundred thousand records

33502.5 -> that you have within XML file document object model

33506.1 -> is not that efficient

33507.337 -> because it's going to load everything into the memory

33510.396 -> which is going to take a lot of time as well as memory,

33513.4 -> which is going to consume a lot of memory.

33515.5 -> So it's not good in terms of time and space complexity.

33518.6 -> Whereas Sachs does a good job when it comes to large xml's

33522.4 -> when it comes to parsing large xml's

33524.594 -> because it's not storing

33526.1 -> or it's not parsing everything into a object in one go.

33530.1 -> It's an event.

33531.028 -> Just so basically you would see

33533.069 -> that it sequentially goes through the XML and as

33536.179 -> and when it sees something right start

33538.549 -> of element start of an attribute or anything of that sort.

33542.2 -> It would give a call to Handler and Handler would process it.

33546.1 -> So basically it's not storing anything.

33548.1 -> It's not retaining any information into memory.

33551.3 -> It is just calling the event handler

33553.4 -> and just leaving it right there.

33555.3 -> So since it's not consuming memory,

33557.755 -> it's good when it comes to large xml's but it's not good

33561.847 -> for random search right random parsing

33564.6 -> because it goes sequentially so for sax parser again,

33568.8 -> you could see the files present

33570.9 -> in Java x dot XML dot parses dot sax parser earlier,

33575.3 -> it was document and here it's sax parser again.

33579.392 -> You could have this Imports done by your ID.

33582.7 -> This is what you event handler is all about.

33585.1 -> Right?

33585.6 -> So you are defining a an event handler here,

33588.129 -> which is nothing but a default Handler

33590.6 -> so Your XML reader using Sachs is nothing

33594.8 -> but a default Handler is a relationship is

33598.553 -> a default Handler you extended your extending default Handler,

33603.556 -> which is maybe an internal interface to your sax parser.

33608 -> Once you extend it.

33609.4 -> It's not an interface or it

33611.14 -> since it's extending it has to be class.

33613.653 -> All right, it's a class.

33615.4 -> So the default parser or the default Handler

33618.8 -> would have this methods within which is nothing

33621.4 -> but start element you have

33623.6 -> characters you have end element and end document.

33627.1 -> So these are the methods within right when you give

33630.4 -> a big XML in this example or when I say this one,

33635 -> so when it comes to student,

33637.2 -> which is your root node,

33638.905 -> it would go to start document when it reads this XML.

33642.9 -> It understands that it's a start of document.

33645.852 -> So it says document begins here.

33648 -> It would go sequentially this parser what it would do.

33651.117 -> Is it would read this entire file

33653.2 -> and it would go sequentially

33655.2 -> when I say sequentially then it would understand

33658.6 -> that there is an element again

33660.878 -> and it would give a call to start element and here

33664.6 -> what you could do is you could print it.

33667.077 -> So what we are doing here is nothing

33669.234 -> but we are printing the XML document using sax parser.

33672.512 -> All right, which is event-based whenever a particular event

33676.3 -> occurs in your XML.

33678 -> It would give a call to the particular Handler.

33680.768 -> So whenever there is a start of document in this case a student

33684.5 -> is a start of element again,

33686.381 -> which would go into start element.

33688.6 -> All right,

33689.2 -> when does it come into characters is nothing

33692.2 -> but when it encounters Henry when it encounters Henry,

33696.7 -> it would go into characters.

33699 -> All right, you see a character's method here.

33701.302 -> It would go into characters and you can see

33703.5 -> that it's a character array.

33705.4 -> Alright, so here it

33707.4 -> would print the entire array which is nothing but the value.

33711.2 -> Lou Henry and all this Leaf nodes.

33713.6 -> All right, Henry Lee and whatever values

33716.662 -> that you have would be printed by this characters method

33720.8 -> whereas the tag names would be printed by your start element

33725.5 -> and end element.

33727 -> This would be your end element.

33728.8 -> All right.

33729.35 -> So this is pretty much like it's an event-driven one,

33732.3 -> whenever it encounters something framework gives a call

33735.6 -> to a particular method

33737.2 -> and this method is user defined

33739.247 -> you could do whatever you want to so this is

33742.037 -> how you create a instance of it.

33744.136 -> So you have sax parser Factory dot new instance

33747.012 -> dot new sax parser.

33748.2 -> You create the instance of sax parser.

33750.3 -> Now you parse it P dot parse

33752.271 -> and you provide the Handler as well then let

33755.3 -> that you have provided

33756.671 -> which is nothing but XML reader using sacks.

33759.222 -> That's your Handler.

33760.4 -> So you have to create the instance of it

33762.5 -> and pass it over.

33763.755 -> Let's see this program now also

33766.14 -> you could see it is reading students dot XML, right?

33770.95 -> So I'll have to change this name to see.

33775.9 -> Ed Eureka XML All right.

33780.4 -> So let's run this program

33782.2 -> which is the same program that I spoke about in the slide,

33785.651 -> which is even based you could see methods implemented

33788.8 -> here and you could see it extending default Handler.

33792.9 -> All right.

33793.4 -> So there's a default Handler this start document

33797 -> basically start document

33798.2 -> and everything is coming from your default Handler.

33802.3 -> All right, and in the start element,

33804.9 -> we are just printing It characters and again

33808.43 -> when it comes to end we are ending it

33811.3 -> and when it comes to end

33812.8 -> of the document we are just printing saying

33815.2 -> that document ends here.

33816.8 -> Alright, so we are reading the same student file

33819.8 -> and this time it's using sacks.

33826.5 -> So you can see here

33827.9 -> when it encountered start of the document.

33830.639 -> It printed document begins here.

33832.7 -> Then you could see elements printed sequentially.

33836.139 -> So this is what it is.

33837.603 -> This is like event-driven right and at the end

33840.8 -> when it reaches the end

33842.1 -> of the document you can see document

33844.266 -> and C are being printed out.

33846 -> So basically this is

33847.344 -> as I said even driven and this is sequential,

33850.3 -> right it goes line by line.

33852.2 -> So if you say you have like a hundred thousand records

33855.6 -> within your XML and say the last entry

33857.92 -> that you are searching

33859.3 -> for it's going to go

33860.8 -> through the entire XML delete encounters the last any

33864.9 -> when it comes to random search or

33867.8 -> if you want to search randomly

33869.958 -> if it's not well suited but when it comes to Big XML,

33873.7 -> it's much better than Tom since it's not loading anything.

33878.1 -> So it's not keeping anything into the memory.

33880.3 -> It's just parsing it it just printing it out

33882.8 -> and it leaves it right there.

33884.7 -> So what are the advantages of Sacks, it is simple.

33888.181 -> It is memory efficient.

33889.851 -> Sax parser is faster than any other parser.

33892.9 -> It handles large document.

33895.3 -> We spoke about all this right here disadvantages of using

33899.607 -> is land will be unable to understand the whole information

33903.992 -> because data is broken into pieces.

33906.7 -> So it's not storing it in one place.

33909.31 -> It's broken into pieces.

33911.1 -> It's not even storing it into memory just flushing it off.

33915.1 -> It's just writing it and leaving it.

33917.2 -> So what's the difference between Dom and sax parser Dom stands

33921.377 -> for document object model Sixth

33923.5 -> and four simple API for XML Dom reads.

33926.8 -> The entire document sacks reads node by node,

33930.164 -> which we saw sequential.

33932 -> It would go Dom is useful

33934.2 -> when reading small to medium-sized xml's Sachs is used

33938.9 -> when big XML files need to be parsed.

33942.9 -> Sax is good for big and this one Dom is used

33946 -> for Two medium sized Dom is tree-based parser.

33950.2 -> We saw it creates a tree and sax is event-based far sir.

33954.73 -> We saw how it has event handler and you saw

33957.923 -> that it calls a particular method based on the event

33961.8 -> that it encounters Tom is little slow as compared to Saks and

33966.7 -> because it has to create the entire tree

33969.3 -> and sax is faster than Dom

33971.9 -> once the tree is created.

33973.6 -> I think Tom would retrieve it much faster than sacks.

33976.836 -> But the tree creation itself takes longer time,

33979.8 -> right when you parse it.

33981 -> It has to create a document model

33983.3 -> which takes a lot of time Dom can insert

33986.2 -> and delete nodes

33987.454 -> since it has entire tree it pre-loaded.

33990.4 -> You could actually go

33991.747 -> and delete it you have the entire tree loaded

33994.532 -> so you can Traverse to any particular node

33997.246 -> and delete a particular node

33999.1 -> or delete a part of a tree itself,

34001.5 -> which means that you could do insertions and deletions

34005.4 -> whereas sack Doesn't store

34007.4 -> anything in memory just reads there

34010.345 -> and just pushes it off.

34012.1 -> So you cannot insert

34013.638 -> or delete nodes into your Source XML.

34016.6 -> So basically it's meant for just doing something

34019.605 -> or retrieving information from your XML.

34022.1 -> It cannot manipulate the source XML sax parser is

34025.604 -> cannot manipulate the source XML now we have one more

34029.4 -> which is Stacks.

34031.5 -> So in terms of sacks,

34033.3 -> if you imagine sex, it's a push API.

34036.2 -> All right,

34037 -> when I say push API it's nothing but it reads through scans

34041.087 -> through the XML and when it encounters an event,

34044.4 -> it pushes the Handler to handle it.

34047.2 -> So there's a push

34048.5 -> from your API to the handler do perform some actions

34052.9 -> whereas Stacks it's a cool API,

34055.8 -> lets go through it to understand more stack stands

34059.32 -> for Java streaming API

34060.9 -> for XML sax parser pulls the required data

34064.3 -> from the XML this Sax parser

34067.4 -> maintains a cursor at the current position

34070.409 -> in the document allows to extract the content available

34074.372 -> at the cursor.

34075.4 -> So basically it maintains the cursor

34077.413 -> at the current position in the document

34079.6 -> which allows it to extract the content available

34082.9 -> at the cursor again,

34084.6 -> you could see Java x dot XML dot stream

34088.2 -> in the first one the Dom we had document the second one.

34091.9 -> We had sacks.

34092.843 -> Now the third one you could see stream.

34095.6 -> So that's the beauty

34096.804 -> of packages you could understand what files are there with them?

34100.615 -> Okay.

34101 -> So using Stacks you could see here.

34103 -> We create an event handler XML element Factory dot create

34107.407 -> XML event handler and new file reader.

34110.236 -> So you pass a new file reader

34112.358 -> and it's nothing but the XML file

34114.7 -> that you want to pass.

34116.3 -> Now, you could see that you get all the elements.

34119.443 -> So basically you have even Trader and you

34122.118 -> get the elements of front

34123.83 -> or you get all the events that you have.

34126.6 -> Then and XML.

34127.8 -> All right and UI thread through it.

34129.8 -> Now you have a switch statement

34131.928 -> which would do the processing for you

34134.3 -> which would say,

34135.3 -> for example, you have a start element similar to

34137.9 -> how we saw in the sax parser.

34140.1 -> So you have a start element and

34142.2 -> if it's a start element and even would be passed

34145.092 -> and you could actually get the element value.

34147.872 -> So basically what we are doing here is we

34150.4 -> are getting all the events and we are iterating through it

34154.167 -> and we have a switch statement which is handling the event.

34157.9 -> So instead of having the event Handler written

34160.807 -> in a separate class.

34162.1 -> We are writing the event handler in the same class.

34165.2 -> This is kind of again decoupling right?

34167.986 -> So imagine yesterday.

34169.402 -> We spoke about comparable and comparator.

34172.1 -> So comparable was like compareto method was written

34175.347 -> within your class right within your model class,

34178.5 -> which was student yesterday.

34180.1 -> All right.

34181 -> And again, we had other example of comparator

34184.2 -> which had a compare method

34186 -> which was Into student objects as an argument.

34189.3 -> So that's the difference.

34190.845 -> Right?

34191.256 -> So we are decoupling it.

34192.9 -> We are writing the entire comparison logic

34195.719 -> to a different class so we can we can imagine the same here.

34199.778 -> So that's what the difference between Stacks and stacks is

34203.7 -> Stacks is writing it within the same class.

34206.9 -> Whereas sacks you have a separate class

34209.8 -> for event handling so you could see here pretty much similar to

34214.5 -> how we did in the sacks

34216.29 -> so you can have like

34217.785 -> if it's a character then you have even -

34220.716 -> characters you print the characters when you

34224 -> encounter and document

34225.674 -> you have event as in document

34227.8 -> and so on basically you get all the events

34230.8 -> and you I trade through it

34232.7 -> and you have switched treatment handling the event.

34235.5 -> All right, so I take this example.

34239.2 -> So the first thing

34240.303 -> that I'll have to do is change the file name.

34244.6 -> Ed Eureka XML and I just run through it.

34261.409 -> Alright, so here we can see start element student.

34265.578 -> You have first element as Henry and so and so forth again,

34270.4 -> first name Henry and stuff like that again.

34273.2 -> You can see the same second student being parsed as well

34276.706 -> which was a dummy student

34278.3 -> that we inserted

34279.5 -> and at the end you will see end of the element student.

34282.9 -> Alright, so this is

34284.261 -> how we parse using three different parsers

34287.4 -> and we saw about advantages

34289.6 -> and disadvantages and which one would be apt one per your use.

34294.2 -> All right.

34294.7 -> So you have to understand the nature of the application

34297 -> or nature of the XML is

34298.6 -> that you are dealing with and based on

34300.8 -> that you could decide which parser to go for

34303.6 -> so that's about the parsers.

34305.488 -> Now, let's talk

34306.5 -> about XPath XPath expression is a query language used to select

34311.1 -> path of XML document based on the query string.

34315.1 -> You can create a query string

34317.33 -> and you can retrieve Wait using X bar X power threatens a node

34322.023 -> set representing XML nodes at the end of the path red.

34326.6 -> So this is basically like wearing language

34329.314 -> or you have X path expression,

34331.3 -> which you could write query in this example.

34334.8 -> If I want to get first name of a student with so-and-so marks

34339.8 -> if I want to get a first name of student

34342.74 -> with 80% marks, right?

34344.4 -> I could do that using XPath.

34346.488 -> So basically it's for querying right

34349.1 -> and it returns a node representing the XML nodes

34352.3 -> at the end of the path.

34353.822 -> It is used to Traverse elements and attributes

34356.8 -> of an XML document XPath defines the structure

34361.383 -> and provides XPath expression.

34363.7 -> So the 7 type of nodes

34365.6 -> that can be output of the execution

34367.781 -> of XPath expression

34369 -> is root element text attribute comment processing instructions

34375.9 -> and namespace.

34378.7 -> We'll take a look at it expert defines a pattern

34382.4 -> or path expression to select nodes

34384.9 -> or node sets in XML document

34387.8 -> what I expect Expressions you have node name,

34391.1 -> which is used to select all nodes

34393.13 -> with the given node name you define a particular node name

34396.847 -> and you could select all the nodes within an XML document

34400.5 -> that has named as node name.

34403.2 -> So it could be either element.

34405.152 -> It could be attribute or anything,

34407.3 -> but it could be just element named rather.

34410.4 -> It specifies that selection starts from the root node.

34414.01 -> If you have 1/4,

34415.1 -> it says that it starts from the root node.

34417.8 -> It specifies that the selection starts from the current node

34421.27 -> that match the selection.

34422.9 -> All right, so /

34424.2 -> scans the entire document / / is nothing but the current node

34428.9 -> dot it is again select the current node.

34431.6 -> So whatever node you are at during parsing,

34434.5 -> it would print it out dot dot is parent node.

34438.5 -> And at the rate is it selects attributes.

34441.6 -> So if you want to carry out certain attributes

34444.6 -> like at the rate ID is equal

34446.5 -> to 10 say the employee IDs been stored as an attribute

34450.234 -> and if you want to have

34451.8 -> employee ID with value hundred you could query out saying

34455.6 -> that at the rate ID is equal

34457.5 -> to hundred steps to use XPath again.

34460.9 -> You have expert related packages.

34463.008 -> You have to import you have to create document filter.

34466.5 -> You have to create an XPath object

34469.1 -> and XPath path expression create a document

34472.83 -> from a file or a stream.

34475.3 -> So basically when you are creating document

34477.8 -> is nothing but it's a dom-based parser.

34480.7 -> Oh, basically it's not well suited for big xml's

34485 -> for small or medium-sized XML.

34487.5 -> It's good enough

34488.595 -> because it's creating document out of your XML then fourth

34492.5 -> create an XPath object and an XPath expression.

34496.9 -> Let's do you have to create object and you have

34499 -> to pass the expression

34500.4 -> that you want to retrieve compile

34502.5 -> the XPath expression first,

34503.8 -> you have to ensure

34504.7 -> that the XPath expression

34506.307 -> that you have provided is up to the mark and it doesn't have

34510.1 -> any error and you're following the contract

34512.9 -> that XPath expression has I'd rate over the list of nodes.

34517.4 -> Once you get the result of the XPath expression

34519.994 -> you have to I'd read through the list of nodes,

34522.7 -> which is nothing but the result and examine attributes

34527.1 -> and examine sub-elements, right?

34530.5 -> That's a typical way in which you would use XPath

34533.7 -> so you could see here.

34535.392 -> It's again Java x dot XML dot X path.

34538.2 -> There is a separate package for it

34540.583 -> and it will have all the classes related

34543.4 -> to it like expat Factory you have constants

34547 -> and you have like exception

34549.4 -> and you have expert class itself here.

34552.8 -> We are again parsing students XML we pass it

34556.379 -> into Document first

34557.9 -> as we mentioned the steps that we spoke about we

34562.1 -> create the document

34563.8 -> and then you apply the XPath you have expression here /

34568.6 -> class / student.

34571.08 -> All right, and then you compile this expression

34574.7 -> what you expression

34576 -> you have here you compile it and you then evaluate it

34579.9 -> so evaluation is nothing but you are retreating

34582.576 -> to the result and you are printing out the result

34585.4 -> that you got to broadly classify.

34588.057 -> What we are doing here is we are creating a document object

34591.9 -> out of the XML file and the next step

34594.6 -> that we do is we compiled the expression

34597.338 -> and then we are evaluating it

34599.4 -> evaluation is nothing but doing something with the result.

34602.9 -> There are a couple of checked exceptions

34604.9 -> that you will have to take care of so you could see

34608.233 -> that it's been handled here.

34610.3 -> It's not specifically handling.

34612.425 -> It is just printing out the stack Trace.

34615.307 -> So let me quickly.

34616.7 -> The take this example.

34619.5 -> Alright, so from here go to resources.

34626.9 -> So let me go to documents downloads.

34637.5 -> And it's let me run through the same example and see

34640.5 -> if it runs.

34647.5 -> Alright, so we have I take

34649.9 -> the same example c letter c at Eureka XML Okay, so,

34669.442 -> let's see if it runs.

34678.2 -> It in fine dot txt size change this to XML.

34685.8 -> Okay, let's try to run.

34687.3 -> So what I am doing here is pretty much passing this XML

34692.6 -> and then reading it through.

34705.2 -> So basically just to again

34707.2 -> tell you I love to see why it's not running at this point,

34710.3 -> but it's more about you just created document model.

34714.2 -> You have your XPath set

34716.2 -> or you have the XPath expression you compile it

34719.119 -> and then you evaluate it which is nothing but

34721.952 -> whatever results you get.

34723.561 -> You can do something on it.

34725.8 -> All right, let me move on to the next slide.

34730.805 -> Dom4j is open source,

34732.5 -> Java based library to parse XML document dom4j is flexible

34736.403 -> and memory efficient.

34737.961 -> It integrates.

34739 -> Well with Tom Sachs apis,

34741.6 -> it should be used when you need the information

34744.9 -> in an XML document more than once.

34747.5 -> So basically with sacks

34749.6 -> if you want to pass through more than once

34752.2 -> if you want the information from the same XML more than

34754.9 -> once it's not that efficient

34756.344 -> because it will have to parse it again.

34758.304 -> So it doesn't store anything.

34759.8 -> It has to go through it again.

34761.6 -> Whereas this one is something

34763.5 -> that integrates well with dom and sax apis,

34766.43 -> which allow developers to use the information

34769.5 -> in an XML document more than once.

34771.903 -> So what are the steps?

34773.6 -> So basically you have to download this dom4j dot jar

34777.336 -> from the website or from the GitHub.

34779.9 -> So there's a GitHub mentioned above so you'll have to go

34782.729 -> and download the latest version from there.

34785.2 -> So once you have that Library,

34787.2 -> this is a common thing that you do in Java.

34790.3 -> You download a jar file.

34791.8 -> You can go and download any particular jar file

34794.717 -> that you opt for when I say jar file.

34797.5 -> It's nothing but the third party Java archive,

34800.5 -> which is nothing but it's a group of classes

34803.4 -> together doing something.

34805.3 -> You can download any jar into a specific directory

34809.3 -> and you can add it into your application.

34812.9 -> There could be a third party say for example,

34816.1 -> I want to add two numbers or say,

34818.5 -> for example, you want to do some big data processing a Java

34822.5 -> by itself doesn't have

34824.012 -> a big data processing library or framework.

34827 -> So what it would do is Big Data framework

34830.2 -> will have a jar file exposed.

34832.43 -> Right which is z for example Apache Apache is a provider

34837.2 -> which is providing solution for big data, right?

34840.514 -> So you would have the libraries

34842.7 -> or you would have everything coded into a jar file

34845.9 -> for big data processing now you need to import that jar file

34849.7 -> into Are you need to link up your application

34852.55 -> to that particular jar file

34854.3 -> to leverage big data processing in application.

34858 -> So in that typical scenario,

34859.4 -> what you do is you would have this jar files downloaded

34862.544 -> into your local directory

34864 -> and have you could add those external jar files

34867.2 -> or this is

34868.1 -> how you link to your applications.

34870.3 -> All right.

34870.8 -> So you go to Java you right click on your application

34874.5 -> go to build path.

34875.9 -> Then you click on Java build path here.

34878.8 -> And then there's a button here to the right

34881.3 -> which is ADD external jars.

34883.5 -> You would have a jar file in this case dom4j

34887.7 -> 2.1 dot o you have this jar files here.

34891.742 -> Now you link up to your application

34894.5 -> and you click on that and you

34896.6 -> click on open that would add the jar file to your application

34900.759 -> and you can apply and close.

34902.7 -> So now you could leverage that particular jar file

34905.582 -> or the functionality

34906.7 -> that is exposed by the jar file into your application.

34910.3 -> All right, in this case,

34911.8 -> it was dom4j introduction to Jack's be Jack's b stands

34916.3 -> for Java architecture for XML binding.

34919.5 -> It's a specification.

34921 -> Actually Jack's be is used to write Java objects into XML

34925.673 -> and vice versa.

34927 -> All right, so you could write it or read it.

34929.7 -> What are the features of Jack speed supports

34932.2 -> for all w3c schema features read

34935.5 -> all the standard w3c standard and all the features

34939.21 -> that you have in w3c.

34940.8 -> It has a support for it.

34942.7 -> It reduces a lot of generated schema derived classes.

34947.4 -> It cut Downs rather

34949 -> on the generated classes scheme are derived classes

34952.334 -> small runtime libraries in terms of size.

34955.93 -> It's pretty lightweight

34957.807 -> it provides additional validation support by jxp,

34961.5 -> 1.3 validation API.

34964.3 -> It steps to convert Java object

34966.7 -> into XML create a pojo or bind the scheme.

34970 -> And generate the classes.

34971.9 -> So basically Jags B is nothing but from the schema,

34975 -> you can create your class.

34977.1 -> All right,

34977.748 -> if you schema says like remember we had

34980.177 -> an excess T wherein we saw

34981.86 -> that it was like an XML which you could read through

34985.133 -> like you could have the schema

34987 -> if you remember we had a student schema

34989.279 -> wherein we declared this is what the format

34991.8 -> of XML would be you could have

34994.11 -> the name you would have student as a starting tag.

34997.9 -> We defined the sequence as well.

34999.628 -> Like first name should be first then last name

35002.16 -> then email address and then marks right?

35004.276 -> We Define the sequence as well.

35006.1 -> So that is nothing but that's a schema.

35008 -> That is XS T.

35009.4 -> So when use Jack's be what you do is from the schema,

35013.448 -> you can create Java classes.

35015.8 -> So basically schema is nothing but schema tells this is

35019.1 -> what an XML can contain and from schema.

35021.791 -> You can have Java classes created

35024 -> so there would be a Java class

35025.853 -> by the name student and within student there would be spring

35029.5 -> so We had the data type Putin in the exist as well.

35032.8 -> Like first name

35033.7 -> would be string last name would be string and stuff.

35036.5 -> There's a mapping between this data type

35038.987 -> and Java data type.

35040.2 -> What it would do is nothing

35041.875 -> but it would create all these properties

35044.279 -> or all the properties

35045.641 -> that you have all the elements of elements

35048.3 -> that you have within student.

35050.291 -> There would be a corresponding property

35052.9 -> created in a Java class.

35054.6 -> So basically this Java class

35056.474 -> could be thought of as a container for your XML,

35059.519 -> right you could parse them into this Java class

35062.5 -> and that's where Jack's be comes into picture.

35065.3 -> It's a binding it binds your XML into this Java classes.

35070.2 -> All right.

35071 -> So create Jack's be context object the

35074.7 -> so the next step is to create Jack's be context object.

35077.4 -> Then create the Marshal ER objects.

35080.3 -> You have to Marshal and unmarshal.

35082.657 -> So in this case,

35083.8 -> since we are going to do from pocho into XML,

35087.1 -> it's going to be Marshall method.

35089.5 -> All right.

35091 -> Create the content free by using set methods.

35095.1 -> All right, whatever.

35096.5 -> You want to set your going to set it into Java object.

35100.113 -> So unlike earlier in the Dom example

35102.5 -> that we took we were actually creating the tree.

35105.096 -> If you remember weapon child and stuff like that,

35107.776 -> which makes it very difficult to understand right

35110.6 -> which is difficult to maintain and if you miss something

35114.11 -> it's cumbersome to actually maintain it.

35116.6 -> Now, you have a student class wherein you just have to set

35120.162 -> into the student class.

35121.6 -> All right, so create the content free by using set methods

35126.111 -> and then call the Marshal method to convert this class

35130.2 -> into an XML.

35132 -> We have a student class and within student class.

35134.4 -> We would have all the properties created

35136.8 -> which is derived from your schema class

35139.3 -> from your schema xsd

35141.3 -> or rather scheming existing mean the same

35144 -> and what you are doing here is

35145.5 -> you are going to set it in to set values

35148.214 -> that you want in the XML in.

35150.242 -> The instance variables in this class student

35153.55 -> and we are going to Marshall it to convert this into XML.

35158 -> So basically rather than creating XML on your own

35161.5 -> what you are doing here is you're using

35163.7 -> the Marshall method to do it.

35165.6 -> So once you Marshall it,

35167.073 -> you should be able to get the XML.

35169.399 -> So let's understand Jason.

35171.892 -> Jason is nothing but JavaScript object notation.

35175.9 -> We will look at the format of it very soon.

35178.7 -> It is easy to read and write than XML XML is bit cumbersome

35183.3 -> when it comes to reading

35185.1 -> and writing and it takes occupies lot of memory as well.

35189.5 -> Jason is language-independent similar to XML.

35193.5 -> It's language independent.

35195.769 -> It is lightweight compared to XML

35198.6 -> and which is nothing but lightweight data

35200.9 -> interchange format XML is a data interchange format as well.

35205.164 -> And Jason is pretty much

35206.9 -> like the same used for data interchange.

35210 -> The medium of communication between two different systems

35213.7 -> Jason supports arrays of objects strings numbers and values.

35219.2 -> So most of the rest API is restful apis,

35222.2 -> which is nothing but a web service built upon HTTP.

35226.2 -> Mostly they use Json for communication between client

35230.5 -> and rest API systems.

35233.2 -> So this is

35234.017 -> because it's pretty lightweight and it's lighter compared to XML

35239.1 -> and as you could imagine

35240.724 -> since it is across networks

35242.479 -> since communication is happening across networks.

35245.6 -> You need to have lightweight system

35247.751 -> or lightweight medium

35249.092 -> or else it would occupy lot of the bandwidth

35251.839 -> between communication just

35253.3 -> because it is lightweight.

35254.6 -> It's preferable interchange format difference between Json

35258.9 -> and XML Json stands

35260.814 -> for JavaScript object notation XML stands

35263.8 -> for extensible markup language.

35266.1 -> Jason is simple to read

35267.683 -> and write XML is difficult to Then rate

35270.3 -> so we have been looking at the examples which were

35272.773 -> not pretty straightforward.

35274.2 -> Right?

35274.8 -> We had a lot of code to be put in

35277.1 -> so it is difficult to read

35279 -> and write Jason is data-oriented XML is document-oriented.

35285.4 -> Jason is less secure than XML XML is more secure

35290.3 -> than Jason Jason supports only text and number data type XML

35296.03 -> supports many data type

35297.8 -> as text number images charts graphs Etc.

35303.8 -> Alright, so it has restriction with the number of data types

35307.3 -> that can hold Json object holds key value pair.

35311.5 -> We took example of student earlier the form of XML, right?

35314.9 -> We're in new head.

35315.965 -> First name last name and marks.

35317.9 -> This is the same example, but in Jason,

35320.8 -> so here you could see opening brace and closing brace

35324.5 -> and you could see student is a key

35327.2 -> and followed by colon and again,

35329.7 -> There's opening brace and closing brace for student

35332.7 -> which means it is saying

35334.6 -> that student is object if you have value

35338 -> as which starts with opening brace,

35341.2 -> which means that the object the second one is

35345.3 -> as you get deep into

35346.8 -> this particular object wherein you see first name, right?

35350.857 -> First name is the key and you see a literal

35353.9 -> which is Henry as object as the value rather and

35358.9 -> as you can see here I Henry is not object.

35361.9 -> That's why you don't have it within braces,

35364.6 -> which means it's a literal value.

35366.7 -> Alright again, you have last name and D'Souza

35369.779 -> which is a literal value you have marks and 50,

35372.956 -> which is a literal value just to summarize whenever you have:

35377.105 -> to the left side of the colon

35379.069 -> is nothing but the key the right side it's a value

35382.3 -> and if you have a value starting with coats,

35385.1 -> which means that it's objects a complex object

35388.022 -> or you have multiple things with

35390.3 -> So in this case,

35391.447 -> you could see that within object.

35393.749 -> You have like three things put in like first name last name

35398.04 -> and marks basically student can be mapped

35401 -> to some object in Java

35402.8 -> which will have first name last name and mouse.

35405.3 -> So each key is represented as string in Jason and key

35409.284 -> is always string in Jason

35411.207 -> and the value can be

35412.745 -> of any type Json array represents order list of values.

35417.7 -> It is always ordered.

35419.3 -> Json array can store string number Boolean or objects.

35425.5 -> It can have string it can hold number it can hold Boolean

35429.882 -> or any other object as well.

35432.2 -> So here you can see

35433.661 -> the first example is array representing days of a week

35438.2 -> and you could see Monday Tuesday Wednesday, Thursday,

35441.2 -> Friday Saturday and Sunday put in there, right you could see

35445.179 -> another example is students

35447 -> and within students you could see it.

35450.3 -> Students is nothing but array of student

35453.8 -> and each student has first name last name email.

35458.5 -> So basically this is how you could interpret it.

35461.1 -> So students is nothing but it's an array.

35464.6 -> So the key is to dance here.

35467 -> Let's see how to run it.

35468.8 -> So the first thing that you do is Jason simple,

35472.7 -> so you can see here jar file is already downloaded

35476.469 -> which I would be using so we have like Jason simple.

35481 -> All right, so it's not there.

35483.1 -> Let me see.

35484.1 -> So whenever you want to deal with Jason's the first thing

35487.586 -> that you would do is you have multiple apis though,

35490.7 -> but the slides to come we are referring

35493.4 -> to Jason simple jar.

35495 -> So the first thing

35496.384 -> that I would do is I would download Jason simple jar.

35501.219 -> All right, so I go.

35507.5 -> So you could go and download this Jason simple jar.

35511 -> Okay, usually nowadays.

35512.769 -> We don't do this

35514.2 -> because we have other we need tools like mavin mavin

35518.248 -> is a build tool

35519.8 -> and you have a file XML file wherein you provide all the jars

35524.022 -> that you want and it would download it by itself.

35527.38 -> So it has got a repository

35529.2 -> from which it would download all the jars.

35531.8 -> You don't have to explicitly put it

35533.8 -> but I don't want to confuse at this point with Maven.

35537.4 -> Let's do it this way downloading it and then linking it.

35541.5 -> All right, so it's connecting.

35543.3 -> Basically, we are downloading the jar, right

35545.901 -> and you could see it has downloaded it.

35548.2 -> It's pretty small like when dkb jar

35550.904 -> because those are all class files.

35553.6 -> It's Java archive,

35555.3 -> which is nothing but class file.

35557.5 -> So I take this and I kind of unzip it.

35564.6 -> Okay, so I get this directory here

35567 -> and you should be able to see a jar file.

35569 -> Now.

35569.248 -> This is nothing but an executable jar file

35571.8 -> you could see it here would see the type as executable jar file.

35575.6 -> All right.

35576.3 -> So now I put it into on let's for Simplicity.

35580.166 -> Let me put it here itself.

35583.3 -> All right, so I create a new folder.

35586.9 -> Which is Ed, Eureka?

35590.4 -> Jason and I put it here.

35593.3 -> So now we'll have to link up our application with that.

35597.6 -> So what I do.

35601.1 -> So when we had this dom4j downloaded

35604.4 -> and linked up we'll have to do the similar stuff

35607.488 -> for this thing as well.

35609.2 -> So since I am using IntelliJ,

35611.8 -> the steps would be different than Eclipse.

35615.4 -> But basically what you do is you go into let

35618.776 -> me see the option here.

35620.967 -> There's open module settings.

35623.2 -> So you go to the open module settings

35625.9 -> and you would see something of this sort coming up.

35630.019 -> Alright, so now I want to add something right.

35634.6 -> Add a particular Library.

35637.311 -> So I go to libraries first.

35639.6 -> I click on add Java and I've Traverse to the path

35644.8 -> that I put the jar file into

35647.1 -> so I put it into Ed Eureka Jason.

35650.488 -> I select this jar file and click on OK.

35654.1 -> So this is basically you're trying to link

35656.488 -> your application to a particular jar file.

35658.953 -> All right, so you could leverage it.

35663.8 -> So here you can see that this is jar file

35666.502 -> that will link to your application.

35669.1 -> All right, I apply it

35671.6 -> which I already did and I will click on OK

35675.8 -> OK, so that's

35676.8 -> how you link any executable jar to your application.

35681.8 -> So you go to the build path you go to this is

35684.842 -> how you do it in Eclipse.

35686.516 -> Like in IntelliJ. I did module settings

35689 -> where as in Eclipse.

35690.215 -> You would go to the build path.

35692.1 -> You would go to the add external jars

35695.1 -> and you would select the path and then apply and close.

35700.103 -> So this is how you do it in Eclipse.

35703.2 -> So encoding Jason in Java,

35706.1 -> how do we encode Jason in Java?

35708.132 -> How do we write a Jason?

35709.834 -> How do we actually create Jason in Java?

35712.4 -> All right.

35713.8 -> So I had to comment this earlier now I uncomment this

35718.2 -> so there was some are earlier now.

35720.5 -> Let me try to resolving it.

35722.5 -> Okay, it's taking So it's asking me which Java class to resolve.

35732.812 -> So there is a Json object class.

35735.446 -> We'll have to see so let me select this one.

35739.4 -> So I have a Json file.

35741.6 -> So similarly, I would prefer just to keep best practices.

35745.7 -> I would say.

35748.6 -> Json object and this is

35751.3 -> like private method the return type is Json object

35755.3 -> and I say create Jason.

35759.6 -> Andre and I would prefer to put this here rather

35763.346 -> than in main method

35765 -> that's one of the best practices by the way,

35767.4 -> it's not something that you have to do.

35770.2 -> But as I said,

35771.145 -> I prefer to write something like this give a meaningful name.

35777.6 -> Something like this.

35779.9 -> So I'm just iterating through this so

35782.4 -> that you get to understand.

35784.4 -> What are the best practices it's not mandatory.

35789.446 -> So I say student.

35791.9 -> Jason then I say student.

35796.2 -> So this is to make it more readable tomorrow

35799.08 -> if I come and look at it.

35800.7 -> I would be able to understand and maybe

35803.1 -> as I said there would be many other developers

35805.711 -> who would be looking at the same code

35807.8 -> that you have written in order

35809.696 -> for them to understand and to increase the maintainability

35813.3 -> and reusability Factor as well.

35815.5 -> It's better to write like this.

35818.4 -> Alright, and then I could even say private void.

35825.4 -> Bring Jason.

35828.361 -> And I take the Json object.

35831 -> You have a print method

35832.769 -> which is taking Json object and say

35835.6 -> I call it as Jason because it could be any generic Jason

35840.7 -> and I print it out saying Jason.

35845.2 -> All right.

35849.5 -> So you have new Json encode a Creator instance of it

35856.3 -> and I create Jason now this Json object.

35864.3 -> Which is nothing but student Jason.

35867.5 -> It's going to be here and I'm going to call new.

35871.3 -> Json encode dot print Jason

35875.9 -> and I'm going to pass the student Jason here.

35882.7 -> So we have created a Json here with first name last name

35886.5 -> and email address and we have marks as well

35890.3 -> and we are printing this Jason there so I have run it.

35894.209 -> Let's see what it shows up.

35896.2 -> So Jason is pretty much light weight as compared to XML

35899.938 -> as you could imagine right XML has all

35902.5 -> this start tag in tag and stuff like that.

35905.3 -> So when it comes to a humongous big chunk of data,

35908.824 -> like millions of data,

35910.475 -> you're processing you could imagine the size

35913.7 -> of Jason is size

35915.1 -> of XML would be pretty much high as compared to Jason

35920.2 -> since Jason is just doing it in the form of key value pair.

35924.2 -> You don't have to end it you don't have the end tags

35927.076 -> and stuff like that when it comes to readability.

35930.4 -> I think in terms of readability XML

35933.1 -> could be better but when it comes to size,

35936.6 -> this one is better.

35937.794 -> Jason is better.

35938.808 -> So machine to machine interaction.

35940.9 -> Jason is better

35942.053 -> whereas Deputy I think XML could be at times more readable

35946.8 -> to humans compared to Jason's.

35949.6 -> Alright, so here you can see Jason being created.

35953.1 -> So again if I want to format this there are online tools

35957.9 -> since this have widely

35959.592 -> become standard for data exchange standards you have lot

35964.8 -> of tools dealing with it.

35966.723 -> All right, if I want to do online tools itself rather

35970.9 -> if I want to do Jason for matter,

35973.15 -> I have Jason for matter as well,

35975.434 -> which is online.

35977.7 -> And it's validating as well.

35979.8 -> If you miss something if you don't have a empty braces,

35983.109 -> or if you don't have a closing brace, it

35985.508 -> would give you an error, right?

35987.349 -> So if I do this,

35988.366 -> you can see that it formatted it

35990.4 -> and it has given you to collapse and expand

35993.3 -> so you could parse through

35995.2 -> and understand more about this Jesus.

35998.3 -> Also, it validates it.

36000.1 -> So if I remove this

36001.4 -> Cody Breeze and

36002.444 -> if I try to do it it would say it's a invalid Jason.

36006.173 -> So if I scroll down it shows invalid Jason

36011.5 -> since it was expecting closing Breeze at the end.

36015.4 -> I put this braces and it should be back up again.

36019.1 -> Be able to parse it.

36020.819 -> All right, so that's about Jason.

36023.819 -> So what do we have next is creating Json file.

36027.4 -> So you could write it into a file.

36029.6 -> Basically what you could convert it is

36031.8 -> into a string and you could write it into a file.

36034.8 -> All right, so if I want to write here Yeah,

36042.9 -> I want to write to file

36046.1 -> and I said Json object for right this Json object into a file.

36052.1 -> What I would do is say I do it using file writer and I

36057.2 -> take the file name as well.

36059.276 -> Say for example or string.

36064.407 -> It should be absolute filename.

36070.3 -> All right, so it's absolute path of the file name.

36073.6 -> So I do F or maybe I can use it within the file writer, right?

36080.4 -> So I create a file writer, which is nothing but Jason.

36085.7 -> File writer since we know

36087.6 -> that it's going to write just Jason's.

36090.8 -> All right.

36091.3 -> I create the instance of it.

36093.007 -> What does it take?

36095.8 -> So we have created a file writer for writing.

36098.512 -> It is showing some exception.

36100.3 -> Remember we have to add exception to throw it.

36104 -> Now.

36104.7 -> What I do is Json file writer. .

36110 -> Right I'm going to write this thing

36114.153 -> Json object as a string.

36116 -> Okay, so Jason dot to Json string.

36120.6 -> All right, I got a string and I would write it into a file.

36124.2 -> Now.

36124.495 -> What I do is Jason brighter dot flush.

36127.223 -> I would flush whatever is been buffered.

36130.9 -> And last thing that I would do is close it.

36135 -> So one thing to remember is you should always close it.

36138.3 -> If you don't close it.

36139.476 -> It's going to remain open

36141.4 -> and which is going to consume lot of your memory at the end

36145.2 -> which might become a bottleneck for your application.

36148.1 -> So remember you whenever you deal with file,

36150.7 -> you have to close it at the end.

36152.7 -> Now what I do is new I create a new instance of Json encode

36159.796 -> and I kind of write to a file.

36162.9 -> Okay write this to a file

36166.2 -> and I need to provide file path as well.

36170.1 -> So I say Ed Eureka.

36173.5 -> Jason died say

36177.507 -> Student Jason I have to handle the exception here as well.

36182 -> If I want handle I can handle it

36184.1 -> or else I can choose to throw it off.

36186.8 -> So in this case, I have thrown it off.

36193.8 -> So you could see the program executed successfully now.

36197 -> Let me go to a director Jason and I see student Jason here.

36202.3 -> Okay, go to see I go to a to record Jason.

36209.2 -> I just open it up and you should be able to see students

36212.9 -> that Jason has all the fields

36214.693 -> that we have gotten right first name marks email

36218 -> and this thing so

36219.7 -> yeah, we saw how to write it into a Json file, right?

36223.042 -> So we have created a Json file

36225 -> and we have similar thing like how to read it

36228 -> from a Json file you have like Json parser,

36231 -> which is again,

36232.1 -> you need to pass your file reader

36234.7 -> and which would pass it into a particular Json object.

36238.8 -> So from your file,

36239.864 -> you are basically converting it into a Json object

36242.8 -> and from Json object.

36244.2 -> You can read whatever data you want to again give you

36248 -> an example you could have private void read Json

36257.8 -> and you could have string say absolute.

36266.586 -> Alright, so you have this now

36268.9 -> what I'm trying to do is I'll create a new Json parser.

36278.9 -> You can see here.

36280.1 -> There's a parse method which takes filereader.

36283.1 -> All right, so I do dot bars.

36287.7 -> All right, and you could see there's a second method here,

36290.6 -> which is taking reader All right.

36292.6 -> So what I do is bars

36297.7 -> new file reader file reader is nothing but is a reader

36303.3 -> that's why you can use it there and I give absolute path name.

36309.4 -> All right, so this should pass your Jason.

36312.4 -> So it's asking me to import it.

36314.421 -> I am putted it.

36316.8 -> So this file not found exception

36318.87 -> that I need to handle which I will rather throw it off.

36322.24 -> Alright, so as you could see here,

36324.317 -> I have thrown of filed all these other exceptional swell

36328.378 -> that I need to handle

36329.7 -> which is nothing but IO exception which is again,

36332.1 -> I've thrown it off.

36333.4 -> Alright, so we have Parts this o on parsing

36336.4 -> what do you get is nothing but object You get Json

36342.4 -> as object right here.

36344.1 -> You have passed it.

36345.4 -> And you have got Jason as object.

36347.618 -> Now.

36347.884 -> What I'm going to do is I'm just print going to print

36351.432 -> say one of the attributes not all since it's going

36354.776 -> to be the same.

36355.8 -> I'm going to print the first name.

36366.5 -> So it says there's no method.

36368.73 -> Let me see.

36369.9 -> So you have this it cannot be taken as object directly.

36375.1 -> It has to be taken as Json object

36377.457 -> so that we could read it.

36379.3 -> All right.

36380.027 -> So this has to be typed costed to Json object.

36383.3 -> This is basically typecasting.

36385.3 -> All right,

36385.994 -> what is typecasting is nothing but you know

36388.985 -> what is going to be written doubt.

36391.4 -> But from the pass is going to be Json object

36395 -> so we can do it something of this sort.

36398.3 -> All right,

36399.1 -> once you do this, you can get based on the key.

36402.6 -> So I give first name key.

36405.3 -> Let me print the last name as well.

36413.384 -> All right, and let me print the email as well

36416.784 -> to for convenience.

36425 -> So basically we are going to read from this so

36428.3 -> its first name last name

36430.3 -> and email as we can see first name is lowercase.

36434.215 -> So this would give an error.

36439.134 -> So we have passed it as well,

36441.5 -> right we have read it from Json file.

36444.4 -> Now.

36444.6 -> What I do is I'll have to give a call to this

36447.4 -> which is nothing but Jason and quote dot read Jason

36454.6 -> and I passed the same file here.

36459.3 -> All right.

36459.8 -> Now it is asking me to handle the exceptions.

36463.242 -> So I add it to the method signature

36466.1 -> as I choose not to handle it.

36468.8 -> All right.

36469.3 -> So what we have done here is nothing but we are we

36471.9 -> are parsing the Json file.

36473.5 -> All right.

36474.192 -> So we have a read Jason method

36476.269 -> which is taking absolute file name as its parameter.

36479.9 -> We have a jsonparser class,

36481.864 -> which is one of the classes from the jar

36484.7 -> that we downloaded Jason simple jar

36487.291 -> that we downloaded

36488.533 -> and since it's put into your application

36491.225 -> since we have attached it with our application.

36494.35 -> We are able to use those classes, right?

36497 -> If you wouldn't have done that step of linking the library

36500.064 -> with the application you won't be able to use this classes.

36503.07 -> Okay, because these are third party classes.

36506.1 -> This is not as a part of the standard Java kit or SDK

36510.161 -> that comes with Java.

36511.9 -> We are to download it and then link it up

36513.9 -> with our application using module settings

36516.2 -> or if you are in an eclipse,

36517.896 -> then it would be configured build path.

36520.2 -> Then you parse it and you provide the reader instance

36524 -> of reader in this case.

36525.612 -> I passed file reader and I give the absolute file name.

36529.4 -> Once this is done you should be able to read messages

36533.4 -> or read the content or read the keys

36537.2 -> that you have within your file.

36539.3 -> You get this an object then I do Json dot get first name then I

36543.592 -> do Jason don't get last name.

36545.6 -> And the last thing that I am printing is email.

36548.8 -> All right.

36549.3 -> Let's see if this works.

36552.23 -> So I'm running this.

36558.2 -> You could see the value being printed here.

36561 -> First name that came out as John then the last name that is Lee

36565.11 -> and the email that we printed.

36567.1 -> That is John at the right one two, three.

36570.2 -> All right,

36570.7 -> so that's about XML and Json which is nothing but it's

36574.7 -> a standard set across industry for data entry exchange.

36578.6 -> So yeah having said

36579.795 -> that one of the main differences between XML

36582.5 -> and Json is its lightweight

36584.218 -> and most of the companies are the industries moving

36587.4 -> towards using Jason's rather than xml's

36590.417 -> but xml's our Legacy

36591.9 -> and they have lot of weed they carry a lot

36594.763 -> of weight in the industries lot of systems at this point.

36598.542 -> I call the financial systems.

36600.522 -> They have Legacy systems and they deal with xml's

36603.789 -> and less of Jesus.

36605.066 -> But Jason is something that is upcoming

36607.752 -> and lot of systems have started migrating

36610.48 -> to or started using Json speak

36612.526 -> since they are lightweight

36614.7 -> that's pretty much it from my sight

36616.7 -> and thanks a lot for Sting

36618.643 -> and I hope you guys all become an emerging coders

36622.232 -> and practice a lot on coding.

36624.615 -> All right, so all the best thank you.

36628.1 -> I hope you have enjoyed listening to this video.

36631 -> Please be kind enough to like it

36633.05 -> and you can comment any of your doubts and queries

36636.2 -> and we will reply them

36637.649 -> at the earliest do look out for more videos in our playlist

36641.417 -> And subscribe to Edureka channel to learn more.

36644.6 -> Happy learning.

Source: https://www.youtube.com/watch?v=hBh_CC5y8-s