8- The Comparable Interface

Jun 21, 2026 09:49 · 4:28 · English · Whisper Turbo · 2 Сөйләүчеләр

Бүгенге көндә бу бинада китапханә эшли. Кайвакытлы саклау өчен яңарту →

Укыту индексы

0:03

S… Speaker 1 (8- The Comparable Interface)

In this video I'm going to show you how to sort data using the comparable interface.

0:07

S… Speaker 1 (8- The Comparable Interface)

So first we're going to add a new class to our collections package.

0:11

S… Speaker 1 (8- The Comparable Interface)

We're going to call that customer.

0:14

S… Speaker 1 (8- The Comparable Interface)

In this class we're going to add a private field,

0:18

S… Speaker 1 (8- The Comparable Interface)

private string,

0:19

S… Speaker 1 (8- The Comparable Interface)

name,

0:19

S… Speaker 1 (8- The Comparable Interface)

and we want to initialize this from the constructor.

0:23

S… Speaker 1 (8- The Comparable Interface)

So we press command and N on Mac or control and N

0:27

S… Speaker 1 (8- The Comparable Interface)

on Windows to bring up the generate palette and select constructor and

0:31

S… Speaker 1 (8- The Comparable Interface)

then select the name field.

0:33

S… Speaker 1 (8- The Comparable Interface)

So, we're initializing this field through our constructor.

0:36

S… Speaker 1 (8- The Comparable Interface)

Super easy.

0:37

S… Speaker 2 (8- The Comparable Interface)

Now,

0:38

S… Speaker 1 (8- The Comparable Interface)

back to our main class,

0:40

S… Speaker 1 (8- The Comparable Interface)

I'm going to create a list of customers.

0:42

S… Speaker 1 (8- The Comparable Interface)

Let's import these types,

0:44

S… Speaker 1 (8- The Comparable Interface)

and then set this to a new array

0:48

S… Speaker 1 (8- The Comparable Interface)

list.

0:49

S… Speaker 1 (8- The Comparable Interface)

Now let's add three customers to

0:53

S… Speaker 1 (8- The Comparable Interface)

this list.

0:54

S… Speaker 1 (8- The Comparable Interface)

So customers .add,

0:55

S… Speaker 1 (8- The Comparable Interface)

here's one customer.

0:57

S… Speaker 1 (8- The Comparable Interface)

I want to set the name to B,

0:59

S… Speaker 1 (8- The Comparable Interface)

another customer with the name A,

1:02

S… Speaker 1 (8- The Comparable Interface)

and finally the last customer with the name C.

1:06

S… Speaker 1 (8- The Comparable Interface)

Now, to sort this list,

1:07

S… Speaker 1 (8- The Comparable Interface)

we can use the collections class.

1:09

S… Speaker 1 (8- The Comparable Interface)

You learned about this earlier.

1:10

S… Speaker 1 (8- The Comparable Interface)

So earlier we talked about the addAll method.

1:13

S… Speaker 1 (8- The Comparable Interface)

Here we have another method for sorting lists.

1:16

S… Speaker 2 (8- The Comparable Interface)

So,

1:17

S… Speaker 1 (8- The Comparable Interface)

we can pass the customer's object over here,

1:20

S… Speaker 1 (8- The Comparable Interface)

but we get a compilation error.

1:23

S… Speaker 1 (8- The Comparable Interface)

No instances of type variables t exists so that customer confirms

1:27

S… Speaker 1 (8- The Comparable Interface)

to comparable.

1:28

S… Speaker 1 (8- The Comparable Interface)

I know this is very confusing.

1:30

S… Speaker 1 (8- The Comparable Interface)

Basically all this is telling us is that the customer class does not implement

1:35

S… Speaker 1 (8- The Comparable Interface)

the comparable interface.

1:36

S… Speaker 1 (8- The Comparable Interface)

Now why does this matter?

1:37

S… Speaker 1 (8- The Comparable Interface)

Well, a lot of sorting algorithms work by comparing objects.

1:42

S… Speaker 1 (8- The Comparable Interface)

So if we can compare two objects,

1:44

S… Speaker 1 (8- The Comparable Interface)

we can determine which object should come first,

1:46

S… Speaker 1 (8- The Comparable Interface)

which one should come next,

1:47

S… Speaker 1 (8- The Comparable Interface)

and so on.

1:48

S… Speaker 1 (8- The Comparable Interface)

So to fix this problem,

1:50

S… Speaker 1 (8- The Comparable Interface)

we should implement the comparable interface in our customer class and that

1:54

S… Speaker 1 (8- The Comparable Interface)

is super easy.

1:55

S… Speaker 1 (8- The Comparable Interface)

You learned this in the last section.

1:56

S… Speaker 1 (8- The Comparable Interface)

So over here we type implements comparable

2:01

S… Speaker 1 (8- The Comparable Interface)

of customer because we

2:06

S… Speaker 1 (8- The Comparable Interface)

want to compare a customer with another customer.

2:08

S… Speaker 1 (8- The Comparable Interface)

Now we press alt and enter and implement this

2:12

S… Speaker 1 (8- The Comparable Interface)

interface.

2:13

S… Speaker 2 (8- The Comparable Interface)

Now,

2:14

S… Speaker 1 (8- The Comparable Interface)

what should we do in this method?

2:17

S… Speaker 1 (8- The Comparable Interface)

Let me quickly refresh your memory.

2:18

S… Speaker 1 (8- The Comparable Interface)

We want to compare two objects.

2:20

S… Speaker 1 (8- The Comparable Interface)

If this object is smaller or less than the other object,

2:24

S… Speaker 1 (8- The Comparable Interface)

we should return a negative value,

2:27

S… Speaker 1 (8- The Comparable Interface)

like minus 1.

2:28

S… Speaker 1 (8- The Comparable Interface)

It could be anything.

2:29

S… Speaker 1 (8- The Comparable Interface)

If these two objects are equal,

2:31

S… Speaker 1 (8- The Comparable Interface)

we should return 0.

2:33

S… Speaker 1 (8- The Comparable Interface)

And if this object is greater than the other object,

2:36

S… Speaker 1 (8- The Comparable Interface)

we should return a positive value.

2:38

S… Speaker 1 (8- The Comparable Interface)

It could be 1 or any positive values.

2:40

S… Speaker 2 (8- The Comparable Interface)

Now,

2:41

S… Speaker 1 (8- The Comparable Interface)

on what basis are we going to compare these customers?

2:43

S… Speaker 1 (8- The Comparable Interface)

Currently,

2:44

S… Speaker 1 (8- The Comparable Interface)

we only have the name field.

2:45

S… Speaker 2 (8- The Comparable Interface)

So,

2:47

S… Speaker 1 (8- The Comparable Interface)

we should compare the name of this customer with the other customer.

2:50

S… Speaker 2 (8- The Comparable Interface)

However,

2:51

S… Speaker 1 (8- The Comparable Interface)

we cannot write code like this,

2:53

S… Speaker 1 (8- The Comparable Interface)

if name is less than o .name.

2:56

S… Speaker 1 (8- The Comparable Interface)

Because this comparison operator can only be applied between numbers

3:00

S… Speaker 1 (8- The Comparable Interface)

and characters,

3:01

S… Speaker 1 (8- The Comparable Interface)

nothing else.

3:02

S… Speaker 2 (8- The Comparable Interface)

So,

3:03

S… Speaker 1 (8- The Comparable Interface)

to solve this problem,

3:04

S… Speaker 1 (8- The Comparable Interface)

we're going to get the name of this customer,

3:07

S… Speaker 1 (8- The Comparable Interface)

this is a string object,

3:08

S… Speaker 1 (8- The Comparable Interface)

it's comparable,

3:09

S… Speaker 1 (8- The Comparable Interface)

so it has the compareTo method.

3:11

S… Speaker 1 (8- The Comparable Interface)

We can compare this with the name of the other customer,

3:15

S… Speaker 2 (8- The Comparable Interface)

so o .name.

3:17

S… Speaker 1 (8- The Comparable Interface)

dot name.

3:17

S… Speaker 2 (8- The Comparable Interface)

Okay?

3:18

S… Speaker 1 (8- The Comparable Interface)

Now whatever value this method returns,

3:21

S… Speaker 1 (8- The Comparable Interface)

we simply return that.

3:22

S… Speaker 2 (8- The Comparable Interface)

Okay?

3:23

S… Speaker 2 (8- The Comparable Interface)

Also,

3:25

S… Speaker 1 (8- The Comparable Interface)

let's rename this parameter to other.

3:27

S… Speaker 1 (8- The Comparable Interface)

That's better.

3:28

S… Speaker 1 (8- The Comparable Interface)

So we're done with the implementation of the comparable interface

3:32

S… Speaker 1 (8- The Comparable Interface)

in our customer class.

3:33

S… Speaker 1 (8- The Comparable Interface)

Now back to the main method.

3:35

S… Speaker 1 (8- The Comparable Interface)

The error is gone.

3:36

S… Speaker 1 (8- The Comparable Interface)

So our list should be sorted.

3:38

S… Speaker 1 (8- The Comparable Interface)

Let's verify it by printing the customer's list on the

3:42

S… Speaker 1 (8- The Comparable Interface)

console. We get this weird strain because

3:47

S… Speaker 1 (8- The Comparable Interface)

This is the default representation of a customer object as a string.

3:51

S… Speaker 1 (8- The Comparable Interface)

We talked about this many times before.

3:53

S… Speaker 1 (8- The Comparable Interface)

So to solve this problem,

3:55

S… Speaker 1 (8- The Comparable Interface)

we should overwrite the toString method in this class.

3:58

S… Speaker 1 (8- The Comparable Interface)

That is super easy.

3:59

S… Speaker 1 (8- The Comparable Interface)

We bring up the generate palette and select toString.

4:04

S… Speaker 1 (8- The Comparable Interface)

Now I'm going to simplify this

4:08

S… Speaker 1 (8- The Comparable Interface)

expression.

4:08

S… Speaker 1 (8- The Comparable Interface)

We only want to return the name of this customer when

4:12

S… Speaker 1 (8- The Comparable Interface)

we try to convert it to a string.

4:14

S… Speaker 1 (8- The Comparable Interface)

Let's run our program one more time.

4:19

S… Speaker 1 (8- The Comparable Interface)

As you can see,

4:19

S… Speaker 1 (8- The Comparable Interface)

our list is sorted.

4:21

S… Speaker 1 (8- The Comparable Interface)

Beautiful.

4:21

S… Speaker 1 (8- The Comparable Interface)

In the next video,

4:22

S… Speaker 1 (8- The Comparable Interface)

we're going to talk about another interface that is used for sorting data.

Бу транскрипция уйлап табылган (автомат сөйләм таныу) ярдәмендә ясалган. Анда хаталар булырга мөмкин - мөһим куллану өчен оригинал аудио белән тикшерегез. AI сәясәт

❤️ STT.aiне яратасызмы?

Тиздән

Бу терминның берничә мәгънәсе бар: Транссибирь тимер юлының Транссибирь бүлекчәсе

Бу транскрипция турында АА-дан сорагыз

Бу ысулның төп өстенлеге — ул җөмләнең эчтәлеген һәм аның эчтәлеген аңлатучы җөмләләрне аерып күрсәтә.

Башкасын күчерү