5- Generics and Primitive Types

Jun 20, 2026 05:32 · 2:24 · English · Whisper Turbo · 2 speakers

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Lecture Index

0:03

S… Speaker 1 (5- Generics and Primitive Types)

When creating an instance of a generic type,

0:05

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we can only use a reference type as a generic type argument.

0:09

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Let me show you what I mean.

0:10

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So I'm going to create a generic list of user.

0:14

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We can pass the user class as a generic type argument because

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this class is a reference type.

0:20

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We can also use the object class or the string class.

0:23

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These are all reference types in java.

0:26

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but here we cannot pass the primitive integer type or short

0:30

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or boolean or float,

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these are all primitive types.

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If you want to store these primitive values inside a generic list,

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we have to use the wrapper class.

0:39

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So every primitive type in Java has a wrapper class,

0:43

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let me show you.

0:43

S… Speaker 2 (5- Generics and Primitive Types)

So,

0:44

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for the primitive int,

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we have the integer class,

0:49

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for the float we have the float class,

0:51

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for the boolean we have the boolean class and so on.

0:55

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So this boolean class is a reference type that stores a boolean value.

1:00

S… Speaker 1 (5- Generics and Primitive Types)

So if you want to create a generic list of integers,

1:03

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we have to write code like this.

1:04

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New generic list of integer.

1:08

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Now let's store this object in a variable of type generic

1:12

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list of integer.

1:13

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Call it numbers.

1:15

S… Speaker 2 (5- Generics and Primitive Types)

Now,

1:17

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look over here.

1:18

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This integer is grayed out because it's unnecessary.

1:22

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We're duplicating our code.

1:23

S… Speaker 2 (5- Generics and Primitive Types)

So,

1:24

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let's remove that.

1:26

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That's better.

1:29

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Now look at the signature of the add method.

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It takes an instance of the integer class,

1:35

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but we can pass a primitive integer like one and the Java compiler

1:39

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will automatically wrap this value inside an instance of

1:43

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the integer class.

1:44

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So it's going to create an instance of the integer class to store this value.

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This process is called boxing.

1:50

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So the Java compiler is going to put this primitive value inside

1:55

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a box.

1:55

S… Speaker 2 (5- Generics and Primitive Types)

Now,

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when we call the get method,

1:59

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look at the return type.

2:00

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We get an instance of the integer class.

2:02

S… Speaker 2 (5- Generics and Primitive Types)

So,

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let's get the first item and store it in a primitive int

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called number.

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Now in this case,

2:10

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the Java compiler is going to extract the value that is stored in that integer

2:14

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object.

2:14

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This is called unboxing.

2:17

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So this is how we can create generic types that work with primitive

2:21

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values.

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