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Boolean Java Tutorial



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in Java there's this term you may have

heard before called boolean it confused

me and it may have confused you but in

this video I'm gonna show you exactly

how to use boolean in Java and if you

watch all the way through you'll have a

fully working program using boolean in

Java hey you it's Alex back again and

helping you learn Java on this channel I

make Java tutorials just like this every

week so if you're new here then consider

subscribing so we're in Eclipse and

we'll just start off our project by

going to file new Java project and we'll

name our project we'll name it something

like boolean in Java and hit OK next

expand that and we're gonna make a file

for our Java code so right click on

source and go to new class class just

means Java file so click that will name

the Java file call it boolean in Java

again hit this first check mark and hit

finish now everything's set up for us

I'll just make this text a little

smaller here a boolean is a variable

just like any other variable like int

for integer string double long float

boolean it's just another kind of

variable so to make a boolean well let's

see how we would make an inch to make a

integer we in Java we would just type

int that's a little keyword it turns

purple and then we'll say we want to

name our integer a and set it equal to

zero that's how we would make an integer

to make a boolean is the exact same

thing except your type boolean like this

this weird word I think they made up

I've never heard it before

before Java and say B equals let's try 0

we get an error here because we can't

declare a boolean as a number it has to

be either true or false

it can only be those two things true or

false nothing else so we can type true

and now B is stored as true the other

option was false so we can type false

and everything works great if we want it

to print out B we can do that

like this be and we'll save it and run

it and we'll see that false gets printed

out we want to print something we want

to print B we go up here we see that B

is equal to false so we print false if

you get one thing away from this video I

want it to be this boolean can only be

true or false well what if it's in

double quotes like this can it be like

that it actually can't because these

double quotes turn it into something

called a string literal which just means

like the literal words not the keyword

FAL se so it can be true or false

it can also be anything that results in

too true or false so it can be like if a

is equal to zero

this works it looks really confusing but

what we're doing here is we're setting a

boolean be equal to the results of

checking if a is equal to zero that's

what the two equal sign means I'll go

over this in a comparison operator video

on the screen now if it's supposed to

get but it's kind of like if we wrap

these in parentheses is equal to zero

looks like it is and so that's true and

so B is now true if we saved it and ran

this it's true little sneak peek into

comparison operators for you so what do

we use boolean for Alex there this funny

word what do we use them for in Java in

my seven years of coding I would say

boolean z'

in Java are mostly used for if

statements I'll go over what if

statements are but first I'll write it

out you type the keyword if and then

parenthesis and curly braces there's a

little red underline here because inside

these parentheses you have to put

something that's true or false sound

familiar

that's a bully so if statements always

have a boolean in the parentheses right

now we'll just pick one of our two

options true or false we'll just pick

true and whenever what is in this

parentheses is true this code will get

run the code that's in these curly

braces so we'll do something simple

like printout we are in the if statement

like that course we'll finish it off

with a semicolon zoom out a little more

here okay good

save it run and see what happens and

look we are in the if statement if I

change this to false save it and run it

nothing happens and we actually get

these yellow underlines and if we check

out the warning it says dead code that

means it never gets reached because it

will never get run since it's false so

the flow here is we have our class we

named it boolean and Java we go inside

and we see this main method the main

method always runs code when we click

the green run-button we see that the

first piece of code in the main method

is this if keyword an if statement works

when what's in this parenthesis is true

this code gets run if it's false it

skips it and doesn't do anything so it

looks like this program does nothing but

if we change this to true like earlier

save and run it we see that it is true

and we do run this and that's mostly

what you use boolean Xin Java for is

passing through if statements and things

similar to if statements now let's write

a program together using boolean angel

we're gonna write a program where we

pass three different doors we go through

the first door and then the second door

and then the third door and those will

be represented as if statements so we

already have our first if statement

we'll say we passed the first door like

that

save and run it we have our first door

next we'll make a second one by just

copying and pasting this since we're

lazy change this to say we passed the

second door and we'll copy and paste

this one more time and say we passed the

third door save it and run it and we get

first second dirt now let's make this a

little more interesting let's say we can

pass a door or we can miss a door

true we passed the door false we missed

the door so we can just represent those

as bullying's remember to make a boolean

is just like any other variable except

we use this funny word bullying will

name it past door and that'll be equal

to true next we'll make a second one

called missed door so we'll name it

missed door and said that one equals

four false the only two options of

bullying can be so now we can have a

little fun with it let's say we want to

pass the first and third door but not

the second we could say passed door and

this is the exact same thing as true so

we didn't really change anything

logically we're just replacing the true

key word with our boolean variable

passed door well skip the second one

we'll say missed door and we'll pass the

third door and type passed door save it

and run it and you'll see that we only

go through the first and third because

this is equal to false so we skip this

code entirely and I'm just gonna zoom

out a little more here on the program so

you can see everything I've been doing a

lot of zooming out my bad let's make

this even more interesting let's say if

you pass all three doors then you win

you win the program so we'll keep track

of how many doors we passed and if we

passed three doors then we'll print a

message saying you want so the counter

would go up one if you're in here you go

up again if you're in here and it go up

again if you're in here so we can use an

integer for that and then add one to it

each time we go through a door so to

make an integer is just like a boolean

just like any other type of variable we

type int and then we'll say door count

as the name of it and we'll set that

equal to zero right now because we

haven't gotten you through any doors yet

if we go through the first door we will

take our door counter

and set it equal to whatever the door

count currently is plus one this is the

same thing as saying our new door count

is equal to the previous door count

which is zero plus one we'll do the same

thing for the second door we'll take our

door counter and we'll take our previous

door count which in this case would be

one and we'll add another one to it and

we'll do that exact same thing down

below but I'll just copy and paste that

the fourth step is if you passed all the

doors if our door count is equal to

three then print the congratulations new

one message but why do that when we

could use boolean in Java make a

variable saying did we win

let's think of a clever name for it it's

a boolean and say let's say I'm passed

all doors good and what's that equal to

false cuz they haven't done that yet but

we know that they passed all doors if

the door count is three so we'll say

passed all doors is gonna be equal to

true once you've passed all three doors

in the door count now we'll just demo

our little program here I'll make this a

little bigger we want to make sure we

pass all the doors remember past door is

just the same thing as true so the code

will get run and it looks like it'll get

run for each if statement here since

they're all true our door count will

keep track of all the doors we entered

and if it's three we'll have passed

doors equal to true so we'll say that

and click this being run button you'll

see we passed the first second and third

like we did before but it's not actually

doing anything because we never printed

the you've one message but we can use

our boolean to see if we passed all of

them so we could say if we passed all

doors

if passed all doors is true that can

only happen if the door count is equal

to three and that can only happen if you

go through

of these doors will say if you pass all

the doors and then I'll print out and

gradual I can't spell

I'm the worst speller there's anyone

else a bad speller leave a comment below

congratulations you won the program you

won the game Frick yeah man Frick yeah

well save it run that and yes you see if

you go through the first door and you

pass the second door and you pass the

third door then we get the message

congratulations you won the program if

we miss one of these say we missed the

first door and change this to mist door

save it and run it we don't get the

congratulations message because the only

pass to but sorry you gotta try again

I'm going to expand this for you because

it's a pretty long program but we're

using a lot of boolean concepts and Java

here a boolean can only be two things it

can only be true or false nothing else

you can do little tricks that results in

true or false and then store that into a

boolean like what we did before where we

could say like is 1 equal to 1 make that

a little neater with some parentheses

take the result of that 1 is equal to 1

so that's true and then sort true into

past or and that's what how it would

happen there so we know bullying's can

be only 2 or false and so we can use

them in if statements and that's what

they're used a lot of the time for

whether we should go inside of an if

statement or just skip right over it in

this case it's skipping right over it

because miss door is equal to false

we'll go to the second one you see that

past door is a variable that holds true

so we'll go in here we'll print this we

pass the second door

and then we'll go to our counter which

takes the previous door count and adds

one to it

do the same thing down here for the

third door if door count is three then

you passed all of them and we'll store

true into the boolean variable pass all

doors if that's true then we know we won

the game and we know we can walk through

we made these jokes on us cuz there's a

key and we had to ninja our way through

the doors and that's why it's so hard if

you enjoyed this video or you think it

might help someone else with boolean and

Java please share it and also like that

click that like button you could be

doing anything in the world but you're

here on this video with me learning how

to program and I appreciate that so much

I'll catch you next week

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