3- The Need for Iterables

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

ບົດບັນທຶກນີ້ຈະໝົດອາຍຸໃນ 24 ມື້ ປັບປຸງໃຫ້ເປັນບ່ອນເກັບທີ່ບໍ່ປ່ຽນແປງ →

Lecture Index

0:03

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

As I told you in the last video,

0:05

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

the iterable interface is at the top of our hierarchy.

0:08

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

Now,

0:09

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

more accurately,

0:09

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

this interface is not part of the collections framework.

0:12

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

In fact,

0:13

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

it's part of the java .lang package.

0:15

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

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

0:19

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

an object that we can iterate or loop over.

0:22

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

Now,

0:23

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

before we look at the specifics of this interface,

0:25

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

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

0:27

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

So here in the main method,

0:29

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

I'm going to create a generic list.

0:31

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

new generic list of strings.

0:34

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

Let's add a couple of objects here.

0:37

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

So add a and b.

0:39

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

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

0:43

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

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

0:47

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

Look,

0:48

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

we have a compilation error here.

0:49

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

For each not applicable to type generic list.

0:52

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

Now,

0:53

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

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

0:58

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

make this private field public.

1:01

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

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

1:05

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

So here in the main method,

1:07

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

we can type list .items now we can iterate over

1:11

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

this array and print each item.

1:13

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

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

1:18

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

implementation of this class to the outside.

1:20

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

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

1:24

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

replace this array with a different data structure

1:28

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

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

1:31

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

As a metaphor,

1:32

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

think of the remote control of your TV.

1:34

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

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

1:38

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

but on the inside,

1:39

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

it has a complex logic board.

1:41

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

That's the implementation detail.

1:43

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

Now,

1:44

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

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

1:48

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

you are not going to get affected.

1:50

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

If they replace a transistor with an advanced model,

1:53

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

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

1:56

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

So changing the internal implementation of a remote control should not

2:00

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

impact its public interface.

2:02

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

In object -oriented programming,

2:04

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

we should design our classes in the same way.

2:06

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

Again,

2:07

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

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

2:10

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

So back to our generic list,

2:12

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

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

2:16

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

detail.

2:17

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

Let me show you the problem with this code.

2:18

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

With this implementation,

2:20

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

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

2:23

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

List that items of zero,

2:26

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

we set this to a string like a,

2:28

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

and then we can print list .items .links.

2:31

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

Now,

2:32

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

what is the problem here?

2:33

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

Well, there is no problem right now,

2:35

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

but if tomorrow we decide to replace this array with

2:39

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

an ArrayList object,

2:40

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

our code is going to break.

2:42

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

Let me show you.

2:43

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

So,

2:43

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

we type ArrayList of t,

2:47

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

this is a class declared in the collections framework,

2:49

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

and it's an implementation of a dynamic array.

2:52

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

We're going to look at it soon.

2:53

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

So let's create an ArrayList object here,

2:56

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

new array list.

2:57

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

Now back to the main method.

3:00

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

See what happened?

3:02

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

Our code broke.

3:04

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

Because the array list class does not support the square bracket

3:08

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

syntax for accessing an object by its index.

3:11

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

Also,

3:12

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

it doesn't have a field called length.

3:16

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

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

3:20

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

resulted in two breaking changes

3:23

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

in our main method.

3:24

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

Now this is a very simple program,

3:26

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

but in a real application,

3:27

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

we could have hundreds of references to our generic list.

3:30

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

So if you change the implementation detail,

3:32

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.

3:36

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

So here's the question,

3:38

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

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

3:42

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

internal implementation?

3:43

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

That is where the iterable interface comes to the rescue.

3:47

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

In the next video,

3:48

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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3- The Need for Iterables

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