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Enhanced For Loop
5:14Let's explore how to loop through all elements in the array using a for each approach.
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So now we have a single variable
that can store multiple elements.
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We can pass that variable around, store it
as a field on an object, but then what?
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In your coding journey, you'll find
that one of the most common tasks in
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programming involves
looping through your data.
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You'll process each and
every value in your data.
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Arrays are wonderful to use for loops.
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So let's go get familiar with them.
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All right, so let's get coding.
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I have attached a new work space here and
there is a file called Explore.java.
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It's got the main boiler plate
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Java application program
already written for you.
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You're welcome.
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So let's take our same
movie theater example
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of getting all these friends together.
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Let's imagine for a second that group
texting doesn't exist because I'm old, and
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I still use one of those flip phones.
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But I wanna send everyone
a text with the movie showtime.
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So let's do this,
let's recreate that friends array here.
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Well, actually, why don't you do it?
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Why don't you use the shortcut method
that you can do when declaring and
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initializing in a single line.
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Here, let's do this,
I'll type out the instructions, let's see.
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Create a new friends array using
the array literal shortcut.
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Include Ben, Alena, and Pasan.
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Okay, pause me, do it and
then unpause me to review how I did it.
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Ready?
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How did you do?
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Here's what I did.
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Made a new string array called friends and
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I added Ben, Alena and Pasan.
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So we want to basically write
a personalized text message to each person
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in our friends array.
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We'll just write out to the console,
but you get the idea.
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Would you wanna process every element in
the array, a great solution to reach for
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is the enhanced for loop.
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The way the enhanced for
loop works is pretty straight forward, so
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first you type the keyword, for.
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Now much like if statements, for
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statements are followed by an expression
which is surrounded by parenthesis.
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And then after you've defined
your expression, again,
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much like an if statement, you open your
block of code with a curly brace and
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close it with a closing curly brace.
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In the enhanced for form,
the expression is pretty clean and clear.
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So what you do first is you declare a new
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variable that you would like
to use within your code block.
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So we're gonna call that String friend.
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And then we're gonna prep the colon and
then friends.
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So this can be read as for
each friend in friends.
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Processing each element of a collection
like this is known as iterating.
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And we are iterating
over our friends array.
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An array is able to be iterated on.
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Or more commonly stated,
arrays are iterable.
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The way that the enhanced for loop works
is that anything that you place over here
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on the right side must be iterable.
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We'll get into how to ensure
that in a future course but for
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now just know that arrays meet
that criteria, they are iterable.
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So, now that we have each element
in the array available on each
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iteration though this loop, we can use it.
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So let's send our pretend text
to each of our friends so,
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let's just use a formatted string, right?
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So let's say System.out.printf,
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let's see, hey %s, the movie starts at 7.
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And remember these flip phones
are hard to type on, so
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I'm just gonna do a C, and a U, and there.
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All right, and
then we're gonna do a new line, %n, cool.
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I'm gonna pass in friend, right?
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Cuz that's what we want to
go in where that %s is.
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So again,
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this friend here is being changed
on each iteration through the loop.
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Each and
every string in this array will run.
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Here, so let's run it.
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So what we'll do is we'll
make sure that this is saved.
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And we'll say clear.
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And javac Explore.java,
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don't need to do that clear but
I like to clear the console before hand.
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And java Explore, and
then that way we can use the up arrow.
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There we go.
We should see, there we go, hey Ben,
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hey Alena, hey Pasan.
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Awesome, so this is pretty clear and
concise, isn't it?
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When you need to process all items in an
array, this enhanced for loop is the way
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to go, and it is the recommended approach
because of how clear it is, right?
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Now you probably notice that this
is called the enhanced for loop.
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So what is this unenhanced for loop then?
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Well, it's just called a for loop,
and let's take a look at that next.
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