Programming a Number Guessing Game - Java Fundamentals
Programming a Number Guessing Game - Java Fundamentals
Remember as a kid when you played “guess a number between 1 and 10”? In this video we’ll program some Java code that simulates playing that game!
My name is Will Tollefson, I’m here to teach you key skills that will help you land your first programming job or stay current and competitive for those promotions in your current job. Subscribe to my channel and I’ll help you grow in your programming skills, and make your career soar!
Join me to learn computer programming in an easy to learn way, with a teacher who isn’t talking over your head. Or sounds like this. But instead explains things in a way you can understand.
I’m a software engineer in industry who has been coding for over a decade now and my motto is Never Stop Learning. I can give you insight into skills that employers actually care about as in addition to being a programmer I also have hired software engineers.
Ring that notification bell so you never miss fresh content that just might help you with your current programming bug.
I have experience with various types of programming such as mobile phone apps, scientific computational modeling, and embedded communications systems, to name a few, and I’ve worked on teams ranging from one to over one hundred programmers.
The content I’m offering you is free, self paced, and practical for computer programming jobs. I’ll teach you skills you need to be competitive.
Let’s dive into programming concepts like algorithms and data structures that are mostly language agnostic.
If you’ve got ideas of topics or a programming dilemma you want me to cover, drop me a comment! I’ll be efficient with your time so without further ado, let’s get to it!
Content
0 -> hi everyone today we're going to be programming a
basic number guessing game within Java it's going
5.4 -> to be building off of some of the things that
we've done in our previous videos where we take
9.72 -> user input and we manipulate it as a kid you
probably played the game hey can you guess a
15 -> number between 1 and 10 or 1 in 100 and then you
had to guess a number and then the person thinking
21.66 -> of the number would tell you higher or lower and
then you would adjust your guess accordingly we're
25.56 -> going to go through how to program that today in
Java what we're going to do is we're going to use
30.48 -> a scanner class like we did in a previous video
and then we're going to also introduce these other
34.86 -> concepts of flow control so let's say that you
want to only execute certain code when a condition
41.76 -> is true or let's say you want to execute some
code repetitively we're going to talk about how
46.62 -> you do that with if else if else cases and while
Loops respectively so without further Ado let's
53.88 -> get into the code all right I've got the IntelliJ
IDE up and I'm going to select a new project and
59.58 -> we're going to call this number guessing in the
code directory add sample code all right that
66.48 -> generated a main class for us with the normal
system.out.printline that I'm going to remove
73.62 -> so the first thing we're going to do is when
you play the number guessing game you've got
77.4 -> two people you've got the person thinking about
the number in their head and then you've got the
81.72 -> guesser so let's figure out what the number that
a player one is going to have in their head we
88.92 -> could just do something like the program always
knows what it is let's say it's always 10. but
96.54 -> let's make it a little more interesting in that
let's make this random so that whenever you play
101.46 -> the game over and over again if you're playing
against yourself it actually stays interesting
105.66 -> we're going to create a random number how do you
do that well similar to how we use the scanner
111.48 -> class what we're going to do is we're going to
use the random class that comes in the Java util
117.06 -> package and we're going to create a random number
from it so you can see here it highlighted Java
122.76 -> util random that looks good so I hit enter there
and that automatically imported the class for us
129.24 -> we're going to go ahead and name this random data
133.68 -> and remember that we need to set it equal
to something because what this is doing
137.52 -> right now is it's only declaring that we have
a variable and not actually giving it a value
142.56 -> so now I'm going to give it uh that Constructor
random I'm going to make a new random instance
151.44 -> that now is held in random data so now I want to
generate a random integer with this random data So
158.28 -> Random data dot next int now if I hover over this
IntelliJ will give me some information on what
165.66 -> that next in method is doing for us right here
this is basically specifying that you could return
172.74 -> any integer value well if I'm playing a number
guessing game I'm not going to be able to easily
177.66 -> guess something within the realm of a couple
billion I would rather guess within something
183 -> that I would find a reasonable range so maybe one
to a hundred something like that so this actually
189.96 -> isn't the function I'm looking for so I'm going
to go ahead and look for a different function
196.14 -> if I search down on next interior I see two
other hits that look interesting this first
202.56 -> one that says bound and then the second one that
says origin and bound this one looks a little more
208.38 -> promising so I'm going to go ahead and do that
one and now I'm going to put in some numbers
214.38 -> origin of one bound of a hundred now if I read
this now this is saying that I'm returning a
221.88 -> pseudorandom generated integer value between
origin inclusive and bound exclusive so when
230.22 -> you play a number game like guess a number between
1 and 10 it's kind of up to you whether 1 and 10
235.92 -> are included in there I would normally think
that they would be so if I want to go from 1
241.5 -> to 100 I actually want to do a hundred plus
one because then that would allow the random
247.38 -> number generator to actually generate a value
of 100 out of this so now that I am generating
252.9 -> a random integer I need to actually store the
value of it notice that this next int function
258.18 -> it says it's public which means I can access
it and then it says in right here that means
263.28 -> that the return of the function is an integer so I
need to capture the return value of this function
271.98 -> like that so we started writing a few lines
274.62 -> of code let's go ahead and
document this with a comment
281.52 -> generate the target number and I actually
don't really like the variable name random
286.86 -> number I'm going to go ahead and call it Target
because that's the target number that player two
291.36 -> should be guessing I want to test to make sure
this code is working properly so I'm going to
296.16 -> type S out which is that shortcut for printing
something to the console I'm going to print out
302.16 -> my target variable I'm going to go ahead and
run this a few times and make sure that I am
306.78 -> getting numbers in the range that I would expect
okay so first time it was 93 second time it was
312.3 -> 41 third time it was 92 fourth time it was 87.
technically there is a little Nuance it's called
318.42 -> pseudo random number generation that's out of
the scope of this video talking about what's
322.8 -> a pseudo random number generate versus a random
number generator but for all intents and purposes
327.6 -> this is generating random data for us within
this range of values cool so now the random
333.18 -> number generator is working let's try to prompt
the user to guess what that random number is
339.06 -> I'm going to go ahead and ask guess
a number between okay so now that I'm
346.56 -> adding format specifiers I need to go to
the print formatted function and percent d
356.94 -> so now um I could go in and duplicate these
variables but I don't want to do that because
365.64 -> now what happens if I want to change this from 1
to 100 to 1 to 90. now I have to know two places
372.78 -> in the code where I would go in and change that
value I don't want to do that I want to create
378 -> variables for this so I only have to store it in
one place I'll do that in lower equals one and
386.82 -> upper equals a hundred now the only thing we have
to do is in the bound since the bound is exclusive
397.86 -> in the next int function we have to still add
one so that we can guess the upper bound exactly
406.32 -> all right now let's go ahead and run this and make
sure this still works all right cool so now it is
410.46 -> prompting us asking for an arm between one and
a hundred but it's not actually waiting for us
415.26 -> to enter anything this is where we need to use
the scanner class that we did last time so we're
421.14 -> going to type scanner hit enter to import it and
we're going to set this equal to a new scanner
428.58 -> instance over system.in just like we did in the
previous video if you have any questions on how
433.14 -> that works go ahead and check out that video now
we're going to get the next integer and we're
440.34 -> going to store that into a variable that we're
going to call guess now let's go ahead and print
446.76 -> out the guess and the target another shortcut
if you want to print a formatted string in
451.2 -> IntelliJ right away is instead of s-o-u-t it's
s-o-u-f let's print the guess and the target
463.2 -> and run this code okay so I guess a number between
100 I'm going to go ahead and put 90. oh actually
468.6 -> it wasn't all that far off my guess was 90 whereas
the random number generator generated 80 there
475.2 -> but it's not telling me that I got the answer
right or wrong necessarily in a message it's
479.94 -> just saying here are the numbers so let's
go ahead and make a conditional logging
485.22 -> statement if we were right or wrong what we
do is this is now some of the flow control
491.34 -> logic that we haven't looked at very much
yet we do what's called an if statement
495.78 -> if we add parentheses for the condition that
we're testing this is a Boolean expression
502.32 -> kind of like how we talked about booleans and
the Primitive types of video we need to provide
506.58 -> the if statement and expression to evaluate if the
statement is true we will go and execute the code
513.6 -> if it's false we will not execute the following
code so we're going to check is is our guess
519.48 -> equal to the Target value now one thing you'll
note here is that single equal sign we use
526.74 -> that when we want to create what's called an
assignment we're assigning a variable to a value
533.28 -> when we have these two equal signs sometimes
called double equals or equals equals
538.86 -> what that means is that these values
need to be exactly the same they look
544.26 -> at equality so let's say these were the same
I'm going to go ahead and print out correct
551.28 -> but what if they weren't the same I can type
else and everything within these brackets
559.32 -> will indicate what I execute when the statement
is not correct let's go ahead and run this I'm
566.22 -> going to go ahead and August 34 this time
well no I wasn't right 29 versus 34. I'm
572.16 -> actually kind of close guys I got off by 10
the first time and off by five the second time
577.62 -> maybe after a while I'll be able to guess it right
on but it's not very fun if I have to rerun the
582.36 -> program every single time I make a guess so why
don't we make this a little more interesting
587.34 -> we'll now add the concept of continuing to Loop
through certain parts of the code until our guess
594.78 -> is correct so how we're going to do that is
we're going to add what's called a while loop
600.36 -> the general concept of a while loop is you
add a condition just like we added a if check
607.98 -> that had a Boolean expression within the
parentheses anything that exists within
614.16 -> the brackets keeps getting executed as
long as the Boolean expression is true
618.9 -> so this code actually could be a real problem
because this will infinitely Loop forever and
624.84 -> never leave you can even see that IntelliJ is
giving us a warning about that while statement
630.24 -> cannot complete without throwing an exception
so now what we want to do is we want to make
634.44 -> this Boolean expression something that
can change within the body of our Loop
639.84 -> so if I'm playing the game I want to keep
playing until I guess the right number right
645.96 -> so you might initially think okay what if
my case is while guess equals Target but
652.56 -> hold on you want to loop as long
as guess is not equal to Target
657.54 -> so the way that you indicate not equal is
you throw an exclamation point in front of it
664.5 -> this means I'm going to Loop in here forever
until guess exactly equals Target but I still
671.4 -> have a few problems here this is indicating that
it can't resolve gas and that's because my guess
676.86 -> variable is down here I'm going to go ahead and
do a keyboard shortcut I'm going to do on Windows
681.18 -> shift control up Arrow and that moves a line of
code up so now it knows what the guess variable is
689.46 -> and I have the target variable but I'm not doing
anything in the while loop So within the bounds of
694.38 -> this Loop guess and Target are never changing so
again this is going to be an infinite while loop
699.54 -> so let's go ahead and prompt the user each
time within the loop to guess a new number
706.08 -> basically I'm going to want this code within my
Loop but I've got a problem here because I already
712.38 -> defined what guess is up here so I'm actually
going to just declare the guess variable without
720.84 -> assigning it a value and then in here I'm going to
assign it a value but you'll notice that the while
726.24 -> loop actually doesn't like that it's saying I have
a guess variable but I haven't initialize it to a
730.8 -> value the reason that that's important is because
when you have a local variable like guess how Java
736.5 -> works is when you don't assign a particular value
to a variable it uses whatever was the default
742.62 -> value at that memory location that the variable
is pointing to which means that this could be
748.74 -> literally anything and there is a tiny tiny chance
that you could happen to have your guess variable
755.1 -> actually equal Target before you even enter
this Loop so that's what this is telling you
759.84 -> so I'm going to go ahead and have this so that it
shouldn't equal Target with my current code I know
765.36 -> that Target has to be in range lower and upper so
if I put a 0 there I know that it's never going
771.6 -> to exit this while loop immediately without
ever executing it so now if we run this code
777.18 -> waiting's gonna happen I'm gonna go
ahead and guess the number I'll guess one
781.26 -> okay my program seems to just be sitting
here it's not doing anything what's going on
787.26 -> I just keep entering numbers okay nothing's
happening so if you think about it we're in
792.42 -> this Loop we're making guesses as long as guess
is not equal to Target we're just going to keep
799.26 -> asking for the next integer from the user
input variable which is reading system.in
806.88 -> I'm not actually telling the user hey your
answer was wrong guess again so I'm going
811.44 -> to go ahead and update this code to do that
so let's check if it was the correct number
817.86 -> guess equals Target
825.24 -> correct otherwise if it wasn't then the
likely event that the guess was wrong
832.14 -> you could say guess again so I'm gonna
go ahead and stop the existing program
836.52 -> and I'm going to try running it again
how's this look guess again okay
844.44 -> so now we're getting somewhere here but typically
how the game works is player one knows the number
850.44 -> and is giggling thinking oh hey you don't
know my number yet and player two is kind of
854.52 -> all right you know give me a hint so player one
says okay you gotta go higher or lower so then
859.14 -> player one can hone in on the area to look
for so let's go ahead and update that next
865.14 -> if guess equals Target we are correct otherwise
we're going to add what's called an else if
873.9 -> so now we add another Boolean expression get
gas is greater than Target you might remember
881.82 -> greater than or less than signs from math class
another thing you can do is you can do an equal
889.5 -> sign but we already know that guess doesn't equal
Target from this Boolean expression above so I'm
895.68 -> going to go ahead and do that guess is equal to
Target guess is greater than Target in this case
905.76 -> so now we want to guess a lower
number because our guess is too high
911.76 -> now the only other case we can
have if the number isn't equal
915.84 -> and it's not greater is that it is less than
so you might think okay I would just write
920.64 -> guess less than Target I know you could
but that's already implied based off of
927.54 -> these previous two Boolean expressions so
you can actually just change this to else
936.36 -> I want to guess higher let's go ahead and stop
this program and run it again all right so now
942.66 -> that I know that I have a number to guess and I
get a higher or lower indication I can use binary
949.44 -> search so I'm going to put my number right in
the middle now I know that is definitely less
953.34 -> than 50. so now if I break that in half again I'm
going to guess 25 . so now it is somewhere between
959.4 -> 25 and 50. so let's try 37. okay now we're really
narrowing down where this could be how about 30.
969.12 -> all right how about 33. there we go all right the
end number was 33 very good so this is an initial
976.98 -> take at how the code could work now let's go in
and make some adjustments to it so first thing
982.14 -> I'm going to do is what am I doing throughout
the branching logic of my code and how can I
986.58 -> go ahead and clean it up it's good to always
comment your code fine upper and lower bounds
1000.2 -> now this code is ask user for first input
1009.14 -> I don't really love this while loop
problem I have with this code is that
1016.28 -> if I set guess equal to zero what happens if
I do something maybe that I shouldn't do and
1024.2 -> I guess a lower bound of zero and an upper
bound of zero if I run this code you'll notice
1033.5 -> that my logic breaks down a little bit uh oh
if I guess a number between zero and zero it
1039.44 -> already says correct and then it prints out
the guess and Target without doing anything
1045.44 -> now this is a bit of an edge case you probably
won't play a game with somebody where you're
1049.82 -> guessing between the same number but let's go
ahead and switch it up let's do zero and one
1057.44 -> now this time the code looks like it's going
to work fine I know that the answer has to be
1061.7 -> one because the code checks for if guess is zero
first so if I run this enough times I will hit
1069.98 -> the situation where it guesses zero immediately
and here it is right here so this is an example
1076.04 -> of where I've got code here that makes certain
assumptions and I've got code here that makes
1081.74 -> certain assumptions and I need to figure out
how to make those assumptions align correctly
1086.54 -> but the main problem I was running into was
that I had to initialize the guess variable
1092.78 -> before I could do it in this wild Boolean
expression there's a way around that and
1098.6 -> that's via what's called a do while loop
so I'm going to go ahead and change this
1106.28 -> into what's called a do wire Loop the main
difference between while and do while is that
1113.24 -> while if the expression is evaluated at the start
and it is already evaluated to false then you
1121.58 -> won't even enter the loop if you have a do while
you guarantee running the loop code at least once
1128.18 -> so now I don't have to give guests an initial
value now the next thing that I notice is that
1136.04 -> when guessed exactly equals Target I get told
correct but I'm already checking that here
1143.84 -> oh and also there's no way this else case can
even exist because the while loop is verifying
1151.28 -> that it keeps looping until guests equals
Target so these are actually not necessary
1159.14 -> but I'm going to change the logic a little bit
I want to limit how big my do while loop is
1166.1 -> so I'm not going to check if guess
equals Target all that I'm going to do
1172.46 -> is check if guess is greater than
Target or gas is less than Target
1181.52 -> so now what this did is I know for a fact
guess has to equal Target to leave the loop
1189.56 -> and the implied else case here is that guess
equals Target so I don't even need to print
1194.84 -> anything I already know what the case is and
sometimes people might want to add a line of
1200.24 -> code explaining that so how the code is written
there's no way I can leave this while loop without
1205.28 -> verifying that this condition is true that's
not always the case when you talk about break
1210.26 -> statements and exceptions but that could be a
topic for a future video but for now I know that
1218.54 -> this is correct and I don't really need to
indicate my guesses anymore so I'm actually
1224.78 -> going to delete that line as well all right so
one last thing that I'm going to mention quickly
1229.52 -> is that the scanner class does have that close
function and a scanner is done close it now in
1241.4 -> my previous video I closed it and that was because
I knew that it was the end of the main function we
1246.14 -> were done with our code this time I'm not going to
close it because I'm going to show that the code
1249.86 -> works just fine without that and in some cases
if there were more code after this that needed
1256.7 -> the system.in resource then you would actually
have an issue where your scanner already closed
1263.6 -> it and now you can't open it anymore so there are
things to think about of when you close a scanner
1268.04 -> and this time I'm just not going to close it just
to give an example of how this still works and
1272.36 -> I forgot to change the range onto something
that's actually more of a fun guessing game
1277.7 -> I'm going to change this from 1 to 10 and
run it again all right look at number seven
1283.4 -> nope one right there how about four cool all right
very good so the last Edition we're gonna make to
1290.06 -> this code is something that's actually near and
dear to my heart and that is friendly competition
1293.72 -> among friends let's say you've got two or three
friends that are all playing this game how quickly
1298.94 -> can you guess the resulting number so to do that
we're gonna make a counter variable that we have
1304.82 -> to initialize outside of the loop because
we're going to use it after the loop is done
1310.64 -> uh we'll go ahead and set it to a value of
zero because we haven't made any guesses yet
1314.6 -> then after each guess attempt we're going to
increment our counter this little plus plus
1320 -> is indicating that you want to add one
onto the value of the counter variable
1325.34 -> so it's going to be 0 here we're going
to make a guess and then it'll be one
1329.42 -> and that is the fastest that somebody could
guess this let's update our print statement
1338.12 -> it took you
1341.66 -> that many tries the reason I'm not doing a
formatted string here just because I've got the
1346.58 -> one variable and I think this is plenty readable
you can go ahead and do a formatted string or you
1352.04 -> can do print line like I've got here all right
so I'm gonna go ahead and try this out it's not
1358.22 -> a three that means it has to be either a one
or a two okay very good that was only two tries
1366.38 -> how about this time nope no okay and that took
me four tries so you can see with not a lot of
1375.38 -> code you actually can make a fun game and you
can play with your friends and while you're at
1380.9 -> it you can show your friends how to write Java
code and hey maybe even introduce them to a
1385.34 -> video like this I'd really appreciate it guys
and that's all there is to it you've written
1390.32 -> another Java program go ahead and check that
as another thing you've done on your list on
1394.82 -> your journey to learning more about Java
congratulations if you like this video or
1398.84 -> want to see more of that type of content
please take a note to like the video and
1403.88 -> write a comment if you found this interesting
if you're enjoying the channel content you
1407.84 -> haven't hit that subscribe button please do take
a moment to do that I really appreciate it well
1413.42 -> that's all I've got for today hope you guys have
a great day and I'll see you next time take care
Source: https://www.youtube.com/watch?v=siogd21nVL4