10- Multiple Type Parameters

Jun 20, 2026 06:47 · 2:32 · English · Whisper Turbo · 2 Cynhadledd

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There are times we want to declare multiple type parameters.

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Here's an example.

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Let's say we want to implement a method for printing a key and a value.

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So in our utils class we type public static void print,

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we give it a key and a value.

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And here we can print key equals value.

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Now,

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in this example we are restricted to integers for keys and values.

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What if you want to pass a string as the key?

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This is not a flexible implementation.

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So just before the return type,

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we add our type parameter and replace the int with

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That's better.

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But again we have a restriction here,

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our values have to be integers.

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This is where we need multiple type parameters.

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So we need to declare a second type parameter.

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Now by convention when we have two type parameters

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We call them K and V as in short for key and

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value.

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This is a common convention.

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But again,

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you could use whatever you wanted.

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It doesn't have to be K and V.

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Now we replace the T with the K and

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the int with the V.

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So back to our main method.

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Let's call utils

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print.

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Now look at the type of these parameters.

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Initially the Java compiler sees both these parameters as objects,

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but we can pass anything here.

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We can pass a primitive value and the Java compiler will wrap this

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inside an integer object.

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For the value we can pass a string,

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we can pass a number,

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we can pass anything.

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So let's run the program,

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we get 1 equals 10.

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Now we can also declare a class with multiple type parameters.

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So,

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here in this project,

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let's add a new class,

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we call it key value pair.

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Now here we add our type parameters,

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so k and v,

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we declare a private field of type k,

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we call it key,

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and another private field of type v call it value.

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Here we can add a constructor to initialize this,

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so public key value pair,

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we need two parameters here,

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key and value.

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And here we set this .key to key and

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this .value to value.

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So this is how we can declare multiple type parameters.

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