5- Generics and Primitive Types

Jun 20, 2026 05:32 · 2:24 · English · Whisper Turbo · 2 Konekte
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When creating an instance of a generic type,
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we can only use a reference type as a generic type argument.
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Let me show you what I mean.
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So I'm going to create a generic list of user.
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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.
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We can also use the object class or the string class.
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These are all reference types in java.
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but here we cannot pass the primitive integer type or short
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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.
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So every primitive type in Java has a wrapper class,
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let me show you.
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So,
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for the primitive int,
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we have the integer class,
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for the float we have the float class,
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for the boolean we have the boolean class and so on.
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So this boolean class is a reference type that stores a boolean value.
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So if you want to create a generic list of integers,
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we have to write code like this.
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New generic list of integer.
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Now let's store this object in a variable of type generic
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list of integer.
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Call it numbers.
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Now,
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look over here.
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This integer is grayed out because it's unnecessary.
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We're duplicating our code.
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So,
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let's remove that.
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That's better.
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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,
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but we can pass a primitive integer like one and the Java compiler
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will automatically wrap this value inside an instance of
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the integer class.
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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.
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So the Java compiler is going to put this primitive value inside
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a box.
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Now,
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when we call the get method,
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look at the return type.
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We get an instance of the integer class.
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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,
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the Java compiler is going to extract the value that is stored in that integer
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object.
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This is called unboxing.
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So this is how we can create generic types that work with primitive
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values.

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