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You have completed Java Loops!
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It’s time to check out the standard for loop, the classic tool for repeating actions a specific number of times using a counter.
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Alright, I hope your brain isn't stuck
0:01
in an infinite loop
trying to process those last two videos.
0:03
I hope they're sinking in
and making sense,
0:06
but if your head feels it's
going to explode, warning.
0:09
This loop we're about to cover might light
the fuse.
0:12
Just remember, these videos
are always here for you to rewatch,
0:15
and you could even slow me way down
if I'm going too fast, okay?
0:19
It's time to meet the classic, the legend,
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the loop you'll see everywhere in Java,
the The standard for loop.
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The standard for loop,
or simply just the for loop, is your go-to
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when you want to repeat something
a certain amount of times
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and you need to keep track
of how many times it's been repeated.
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You tell it where to start, when to stop,
and how to count,
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and it takes care of the rest.
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The syntax might look a
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little intimidating at first,
but it's actually pretty logical.
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Let's torture our brains a bit, shall we?
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Okay, go ahead and launch the workspace
again if you don't have it open still.
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Let's open up For.java.
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Let's go into the main method here,
and here's the basic structure.
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We type for, some parentheses
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for the condition,
and curly braces for the body.
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Just the normal while loop, right?
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That's not so bad.
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The reason this tends to be overwhelming
at first is this conditional section
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here actually ends up holding
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three separate expressions,
and they need to be in a specific order.
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Let's just get right into it.
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For this example,
let's recreate what we did in that first
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while loop, you know,
where we were sneaking all those cookies.
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I'm kind of hungry for tacos now, though.
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The first of the
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three expressions is what is known
as the initialization expression.
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The variable you initialize
here is only in the for loop's scope.
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So what we want to do is create,
or initialize,
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an integer
that will work as our counter variable.
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For loops really shine when used
with arrays and other collections,
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and usually you'll see this variable named
I, short for index.
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And it will usually start at zero
since arrays have a zero-based index.
2:02
Now, don't worry about all that stuff
for now, you'll learn about arrays
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soon enough and you'll likely experience
the true power of this loop.
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For now, let's name
our integer tacosEaten.
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And like we did with the
cookies before, let's set it
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equal to zero, because we just sat down,
we haven't eaten anything yet.
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We end this
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first expression with a semicolon.
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Okay, now the second expression,
the conditional.
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This is where we tell the loop
when it stops.
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This is going to be checked
before every cycle of this loop.
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So real quick, let's create a variable up
top here
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and say int total tacos equals 3.
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This is the max amount
we're allowed to eat.
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Bummer, I know.
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Alright, after the first expression's
semicolon, we'll write tacos eaten
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less than total tacos
and add another semicolon.
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So far so good, right?
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Let's keep pushing
and we'll break it all down again later.
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Okay, the final condition is the increment
or stepping expression.
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This is run after every completed run
through the loop.
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We want to increment our counter here,
so we'll say
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tacosEaten++, and we don't need
a semicolon after this one.
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Now this is
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very long, and that's partially my fault.
3:20
No need to follow me here but real quick
I'll show you what you typically see with
3:24
for loops out there in the wild.
Usually you have int i equals zero
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i is less than something,
usually an array's
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length, i plus plus.
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So it's typically much shorter,
but I'm trying to be verbose
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and very clear here
for your first introduction.
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Okay, inside the body,
I'll just go system.out.println.
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Ooh, a taco.
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Om, nom, nom, nom, nom.
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Eating sounds there, you know.
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All right, let's break
this whole thing down again.
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We write our for.
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Then as our first expression,
we initialize
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a counter variable as an integer,
and we start it at 0.
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This expression
only runs once, before anything else.
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The second expression is then checked.
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Is 0 less than 3?
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Yes, it is. So let's run our code below.
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We'll print that line, and afterwards,
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we come back up to this third expression,
incrementing our variable.
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So now it's equal to 1.
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We go back here and check again.
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Is 1 less than 3? Yep.
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Let's run the code again.
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Prints this line, goes up here,
and now our variable is 2.
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Is 2 less than 3?
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Indeed it is.
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Let's print that line, increment
our variable, and now it's 3.
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Is 3 less than 3? Nope.
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Let's terminate this for loop
now, and it's done.
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I hope that's clear,
and at least slightly makes sense.
4:50
Like I said, rewatch this video anytime
you need to, and when we get into arrays,
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you'll get much more practical practice
with this.
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Let's run this bad boy.
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Clear and javac For.java
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and java For. Okay.
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Ooh a taco, three times. Perfect!
5:11
I really
want to drive home the syntax here
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so let's do another example
in a slightly different way
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to really show what you can do with these.
We'll be decrementing this time
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and showing that variable as i,
like you'll see more often than not.
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Let's pretend we work for a space station
and we're
5:30
counting down our space rocket launch.
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Let's say for,
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and this time we'll say int i equals 5.
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For the condition,
we'll check before every loop
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if i is greater than 0.
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Lastly, we'll decrement this time with
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i minus minus.
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In the body, we'll say system.out.println
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and just provide
i, which is our counter variable here.
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So every loop,
it should be going down by 1 from 5.
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After the loop closes,
we'll say system.out.print, lift off.
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Alright, let's run this
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again and see if it works.
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Awesome.
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We started at 5, went to 4, 3, 2, 1,
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and after that loop, it decremented
i to 0.
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Then it checked, is 0 greater than 0?
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It realized
it wasn't and terminated the loop.
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Whew!
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That probably felt a lot, I know.
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Try not to let this overwhelm
you too much.
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As I stated earlier,
these become really useful when working
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with arrays and other collections,
which you'll get into soon.
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Now when you do get there,
this will look familiar
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and it won't be such a brain shock
while also trying to learn arrays.
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In the next video, we're going
to check out another way of iterating
6:50
over a collection,
but in a much simpler syntax.
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I'll see you there.
6:56
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