3- A Poor Solution

Jun 20, 2026 04:56 · 3:22 · English · Whisper Turbo · 2 speakers

Transkrip ini luput dalam 24 hari. Naik taraf untuk storan kekal →

Lecture Index

0:03

S… Speaker 1 (3- A Poor Solution)

One way to solve the problem in the last video is to use an area of objects here

0:07

S… Speaker 1 (3- A Poor Solution)

because the object class is the base or the parent of all reference types

0:11

S… Speaker 1 (3- A Poor Solution)

in Java.

0:12

S… Speaker 1 (3- A Poor Solution)

Remember reference types?

0:13

S… Speaker 1 (3- A Poor Solution)

We talked about them in the first part of this series.

0:16

S… Speaker 1 (3- A Poor Solution)

To refresh your memory,

0:17

S… Speaker 1 (3- A Poor Solution)

we have two categories of types in Java.

0:20

S… Speaker 1 (3- A Poor Solution)

Primitive types and reference types.

0:22

S… Speaker 1 (3- A Poor Solution)

Primitive types are numbers,

0:24

S… Speaker 1 (3- A Poor Solution)

characters,

0:24

S… Speaker 1 (3- A Poor Solution)

and booleans.

0:25

S… Speaker 1 (3- A Poor Solution)

Everything else is a reference type.

0:27

S… Speaker 1 (3- A Poor Solution)

So if we use an array of objects here,

0:29

S… Speaker 1 (3- A Poor Solution)

we can store anything in this array.

0:31

S… Speaker 1 (3- A Poor Solution)

For example,

0:32

S… Speaker 1 (3- A Poor Solution)

we can store user objects because the user class extends the object

0:36

S… Speaker 1 (3- A Poor Solution)

class.

0:36

S… Speaker 1 (3- A Poor Solution)

So let's replace all these integers with the object class.

0:39

S… Speaker 1 (3- A Poor Solution)

So here we have an object array and here

0:44

S… Speaker 1 (3- A Poor Solution)

as well, the parameter of the add method should be an object and

0:48

S… Speaker 1 (3- A Poor Solution)

also the return type of the get method should be an object.

0:53

S… Speaker 2 (3- A Poor Solution)

Now,

0:54

S… Speaker 1 (3- A Poor Solution)

back to our main class.

0:56

S… Speaker 1 (3- A Poor Solution)

We can store numbers in this array.

0:58

S… Speaker 1 (3- A Poor Solution)

We can also store strings.

1:01

S… Speaker 1 (3- A Poor Solution)

We can also store user

1:05

S… Speaker 1 (3- A Poor Solution)

objects.

1:05

S… Speaker 1 (3- A Poor Solution)

So that's great,

1:08

S… Speaker 1 (3- A Poor Solution)

isn't it?

1:08

S… Speaker 1 (3- A Poor Solution)

Not really.

1:09

S… Speaker 1 (3- A Poor Solution)

This is a very bad solution for a couple of reasons.

1:12

S… Speaker 1 (3- A Poor Solution)

But before we talk about these reasons,

1:13

S… Speaker 1 (3- A Poor Solution)

I've got a question for you.

1:15

S… Speaker 1 (3- A Poor Solution)

Earlier I told you that the object class is the parent of all reference

1:19

S… Speaker 1 (3- A Poor Solution)

types, so we can store any objects in this list.

1:21

S… Speaker 1 (3- A Poor Solution)

However,

1:22

S… Speaker 1 (3- A Poor Solution)

this integer here,

1:23

S… Speaker 1 (3- A Poor Solution)

this is a primitive value,

1:25

S… Speaker 1 (3- A Poor Solution)

it's not an object,

1:26

S… Speaker 1 (3- A Poor Solution)

it's not a reference type.

1:27

S… Speaker 1 (3- A Poor Solution)

So how can we store it here?

1:29

S… Speaker 2 (3- A Poor Solution)

Well,

1:30

S… Speaker 1 (3- A Poor Solution)

when we compile this code,

1:31

S… Speaker 1 (3- A Poor Solution)

the Java compiler will convert this code to something like this.

1:35

S… Speaker 1 (3- A Poor Solution)

Integer dot value of 1.

1:38

S… Speaker 1 (3- A Poor Solution)

So we have this integer class in Java,

1:40

S… Speaker 1 (3- A Poor Solution)

it's a reference type,

1:41

S… Speaker 1 (3- A Poor Solution)

it derives from the object class.

1:43

S… Speaker 1 (3- A Poor Solution)

And this class has a static method,

1:45

S… Speaker 1 (3- A Poor Solution)

valueof,

1:46

S… Speaker 1 (3- A Poor Solution)

which returns a new instance of the integer class.

1:50

S… Speaker 1 (3- A Poor Solution)

So this is the reason why we can pass a primitive value to this method.

1:54

S… Speaker 1 (3- A Poor Solution)

By the same token,

1:55

S… Speaker 1 (3- A Poor Solution)

we have a wrapper class for every primitive type in Java.

1:59

S… Speaker 1 (3- A Poor Solution)

We have float,

2:00

S… Speaker 1 (3- A Poor Solution)

we have double,

2:01

S… Speaker 1 (3- A Poor Solution)

boolean,

2:02

S… Speaker 1 (3- A Poor Solution)

character,

2:03

S… Speaker 1 (3- A Poor Solution)

and so on.

2:04

S… Speaker 2 (3- A Poor Solution)

Okay,

2:05

S… Speaker 1 (3- A Poor Solution)

so let's revert this back.

2:08

S… Speaker 1 (3- A Poor Solution)

What are the problems with this implementation?

2:10

S… Speaker 2 (3- A Poor Solution)

Well,

2:11

S… Speaker 1 (3- A Poor Solution)

the first problem is that if you want to get the first item in this list,

2:13

S… Speaker 1 (3- A Poor Solution)

we call the get method.

2:16

S… Speaker 2 (3- A Poor Solution)

Now,

2:18

S… Speaker 1 (3- A Poor Solution)

we know that this is an integer,

2:19

S… Speaker 1 (3- A Poor Solution)

so we may hope to store it in an integer variable called number.

2:23

S… Speaker 1 (3- A Poor Solution)

but we have a compilation error because this get method returns an object,

2:28

S… Speaker 1 (3- A Poor Solution)

but we expect an integer.

2:29

S… Speaker 1 (3- A Poor Solution)

So here we have to explicitly cast the result to

2:34

S… Speaker 1 (3- A Poor Solution)

an integer.

2:34

S… Speaker 1 (3- A Poor Solution)

And this makes our code a little bit verbose and noisy.

2:37

S… Speaker 1 (3- A Poor Solution)

The second problem is that if we use the wrong type here,

2:40

S… Speaker 1 (3- A Poor Solution)

we'll get an invalid cast exception.

2:42

S… Speaker 1 (3- A Poor Solution)

For example,

2:43

S… Speaker 1 (3- A Poor Solution)

let's change 0 to 1.

2:45

S… Speaker 1 (3- A Poor Solution)

We know that the second item in this list is a string.

2:48

S… Speaker 1 (3- A Poor Solution)

What if we accidentally try to cast it to an integer?

2:51

S… Speaker 1 (3- A Poor Solution)

We run our program,

2:55

S… Speaker 1 (3- A Poor Solution)

we get a class cast exception.

2:59

S… Speaker 1 (3- A Poor Solution)

Now the problem here is that we will not be aware of bugs like this

3:03

S… Speaker 1 (3- A Poor Solution)

until we run our application and test all the functions.

3:06

S… Speaker 1 (3- A Poor Solution)

So we can only identify these problems at runtime.

3:09

S… Speaker 1 (3- A Poor Solution)

It would be great if we could catch these problems at compile time.

3:13

S… Speaker 1 (3- A Poor Solution)

And that's what generics are for.

3:15

S… Speaker 1 (3- A Poor Solution)

In the next video,

3:17

S… Speaker 1 (3- A Poor Solution)

I will show you how generic classes help us solve these problems.

This transcript was generated by AI (automatic speech recognition). May contain errors — verify against the original audio for critical use. AI policy

❤️ Love STT.ai? Tell your friends!

Ringkasan

Klik Ringkasan untuk mencipta ringkasan AI transkripsi ini.

Tanya AI Tentang Transkrip Ini

Tanya apa-apa tentang transkripsi ini — AI akan cari bahagian yang berkaitan dan menjawab.

Tulis Semula Lain