3- The Need for Iterables

Jun 20, 2026 07:51 · 3:54 · English · Whisper Turbo · 2 speakers

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S… Speaker 2 (3- The Need for Iterables)

As I told you in the last video,

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S… Speaker 2 (3- The Need for Iterables)

the iterable interface is at the top of our hierarchy.

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S… Speaker 1 (3- The Need for Iterables)

Now,

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S… Speaker 2 (3- The Need for Iterables)

more accurately,

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S… Speaker 2 (3- The Need for Iterables)

this interface is not part of the collections framework.

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S… Speaker 2 (3- The Need for Iterables)

In fact,

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S… Speaker 2 (3- The Need for Iterables)

it's part of the java .lang package.

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S… Speaker 2 (3- The Need for Iterables)

So it's one of the fundamental interfaces in Java and represents

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S… Speaker 2 (3- The Need for Iterables)

an object that we can iterate or loop over.

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S… Speaker 1 (3- The Need for Iterables)

Now,

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S… Speaker 2 (3- The Need for Iterables)

before we look at the specifics of this interface,

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S… Speaker 2 (3- The Need for Iterables)

let's talk about the problem it tries to solve.

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S… Speaker 2 (3- The Need for Iterables)

So here in the main method,

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S… Speaker 2 (3- The Need for Iterables)

I'm going to create a generic list.

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S… Speaker 2 (3- The Need for Iterables)

new generic list of strings.

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S… Speaker 2 (3- The Need for Iterables)

Let's add a couple of objects here.

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S… Speaker 2 (3- The Need for Iterables)

So add a and b.

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S… Speaker 2 (3- The Need for Iterables)

Now we want to iterate over this list and print each item.

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S… Speaker 2 (3- The Need for Iterables)

So we write a for each loop for item in list.

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S… Speaker 1 (3- The Need for Iterables)

Look,

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S… Speaker 2 (3- The Need for Iterables)

we have a compilation error here.

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S… Speaker 2 (3- The Need for Iterables)

For each not applicable to type generic list.

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S… Speaker 1 (3- The Need for Iterables)

Now,

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S… Speaker 2 (3- The Need for Iterables)

one way to solve this problem is to go back to the generic list class and

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S… Speaker 2 (3- The Need for Iterables)

make this private field public.

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S… Speaker 2 (3- The Need for Iterables)

then we'll be able to access the items array from outside of this class.

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S… Speaker 2 (3- The Need for Iterables)

So here in the main method,

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S… Speaker 2 (3- The Need for Iterables)

we can type list .items now we can iterate over

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S… Speaker 2 (3- The Need for Iterables)

this array and print each item.

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S… Speaker 2 (3- The Need for Iterables)

Now the problem with this approach is that we have exposed the internal

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S… Speaker 2 (3- The Need for Iterables)

implementation of this class to the outside.

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S… Speaker 2 (3- The Need for Iterables)

So if we decide to change this implementation in the future and

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S… Speaker 2 (3- The Need for Iterables)

replace this array with a different data structure

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S… Speaker 2 (3- The Need for Iterables)

All the code that is dependent on this field will have to be changed.

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S… Speaker 2 (3- The Need for Iterables)

As a metaphor,

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S… Speaker 2 (3- The Need for Iterables)

think of the remote control of your TV.

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S… Speaker 2 (3- The Need for Iterables)

This remote control has a few simple buttons for you to work with,

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S… Speaker 2 (3- The Need for Iterables)

but on the inside,

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S… Speaker 2 (3- The Need for Iterables)

it has a complex logic board.

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S… Speaker 2 (3- The Need for Iterables)

That's the implementation detail.

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S… Speaker 1 (3- The Need for Iterables)

Now,

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S… Speaker 2 (3- The Need for Iterables)

if tomorrow the manufacturing company decides to change this internal implementation,

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S… Speaker 2 (3- The Need for Iterables)

you are not going to get affected.

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S… Speaker 2 (3- The Need for Iterables)

If they replace a transistor with an advanced model,

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S… Speaker 2 (3- The Need for Iterables)

you can still use the same buttons you're familiar with.

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S… Speaker 2 (3- The Need for Iterables)

So changing the internal implementation of a remote control should not

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S… Speaker 2 (3- The Need for Iterables)

impact its public interface.

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S… Speaker 2 (3- The Need for Iterables)

In object -oriented programming,

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S… Speaker 2 (3- The Need for Iterables)

we should design our classes in the same way.

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S… Speaker 1 (3- The Need for Iterables)

Again,

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S… Speaker 2 (3- The Need for Iterables)

I talked about this concept a lot in the second part of this series.

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S… Speaker 2 (3- The Need for Iterables)

So back to our generic list,

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S… Speaker 2 (3- The Need for Iterables)

we should not expose the items filled to the outside because this is the implementation

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S… Speaker 2 (3- The Need for Iterables)

detail.

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S… Speaker 2 (3- The Need for Iterables)

Let me show you the problem with this code.

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S… Speaker 2 (3- The Need for Iterables)

With this implementation,

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S… Speaker 2 (3- The Need for Iterables)

we can go back to our main method and write code like this.

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S… Speaker 2 (3- The Need for Iterables)

List that items of zero,

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S… Speaker 2 (3- The Need for Iterables)

we set this to a string like a,

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S… Speaker 2 (3- The Need for Iterables)

and then we can print list .items .links.

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S… Speaker 1 (3- The Need for Iterables)

Now,

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S… Speaker 2 (3- The Need for Iterables)

what is the problem here?

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S… Speaker 2 (3- The Need for Iterables)

Well, there is no problem right now,

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S… Speaker 2 (3- The Need for Iterables)

but if tomorrow we decide to replace this array with

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S… Speaker 2 (3- The Need for Iterables)

an ArrayList object,

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S… Speaker 2 (3- The Need for Iterables)

our code is going to break.

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S… Speaker 2 (3- The Need for Iterables)

Let me show you.

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S… Speaker 1 (3- The Need for Iterables)

So,

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S… Speaker 2 (3- The Need for Iterables)

we type ArrayList of t,

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S… Speaker 2 (3- The Need for Iterables)

this is a class declared in the collections framework,

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S… Speaker 2 (3- The Need for Iterables)

and it's an implementation of a dynamic array.

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S… Speaker 2 (3- The Need for Iterables)

We're going to look at it soon.

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S… Speaker 2 (3- The Need for Iterables)

So let's create an ArrayList object here,

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S… Speaker 2 (3- The Need for Iterables)

new array list.

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S… Speaker 2 (3- The Need for Iterables)

Now back to the main method.

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S… Speaker 2 (3- The Need for Iterables)

See what happened?

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S… Speaker 2 (3- The Need for Iterables)

Our code broke.

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S… Speaker 2 (3- The Need for Iterables)

Because the array list class does not support the square bracket

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S… Speaker 2 (3- The Need for Iterables)

syntax for accessing an object by its index.

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S… Speaker 1 (3- The Need for Iterables)

Also,

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S… Speaker 2 (3- The Need for Iterables)

it doesn't have a field called length.

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S… Speaker 2 (3- The Need for Iterables)

So a simple change in the implementation detail of our generic list

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S… Speaker 2 (3- The Need for Iterables)

resulted in two breaking changes

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S… Speaker 2 (3- The Need for Iterables)

in our main method.

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S… Speaker 2 (3- The Need for Iterables)

Now this is a very simple program,

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S… Speaker 2 (3- The Need for Iterables)

but in a real application,

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S… Speaker 2 (3- The Need for Iterables)

we could have hundreds of references to our generic list.

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S… Speaker 2 (3- The Need for Iterables)

So if you change the implementation detail,

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S… Speaker 2 (3- The Need for Iterables)

then we'll have to go back and fix all those hundreds of places that are broken.

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S… Speaker 2 (3- The Need for Iterables)

So here's the question,

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S… Speaker 2 (3- The Need for Iterables)

how can we iterate over a list without knowing anything about its

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S… Speaker 2 (3- The Need for Iterables)

internal implementation?

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S… Speaker 2 (3- The Need for Iterables)

That is where the iterable interface comes to the rescue.

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S… Speaker 2 (3- The Need for Iterables)

In the next video,

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S… Speaker 2 (3- The Need for Iterables)

I'm going to show you how to solve this problem using the iterable interface.

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