10- Multiple Type Parameters
Jun 20, 2026 06:47
· 2:32
· English
· Whisper Turbo
· 2 Speaker
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Speaker 1 (10- Multiple Type Parameters)
There are times we want to declare multiple type parameters.
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Here's an example.
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Speaker 1 (10- Multiple Type Parameters)
Let's say we want to implement a method for printing a key and a value.
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Speaker 1 (10- Multiple Type Parameters)
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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Speaker 2 (10- Multiple Type Parameters)
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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Speaker 1 (10- Multiple Type Parameters)
This is not a flexible implementation.
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Speaker 1 (10- Multiple Type Parameters)
So just before the return type,
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we add our type parameter and replace the int with
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Speaker 1 (10- Multiple Type Parameters)
t.
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Speaker 2 (10- Multiple Type Parameters)
That's better.
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Speaker 1 (10- Multiple Type Parameters)
But again we have a restriction here,
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our values have to be integers.
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Speaker 1 (10- Multiple Type Parameters)
This is where we need multiple type parameters.
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Speaker 1 (10- Multiple Type Parameters)
So we need to declare a second type parameter.
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Speaker 1 (10- Multiple Type Parameters)
Now by convention when we have two type parameters
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Speaker 1 (10- Multiple Type Parameters)
We call them K and V as in short for key and
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Speaker 1 (10- Multiple Type Parameters)
value.
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Speaker 1 (10- Multiple Type Parameters)
This is a common convention.
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Speaker 2 (10- Multiple Type Parameters)
But again,
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Speaker 1 (10- Multiple Type Parameters)
you could use whatever you wanted.
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Speaker 1 (10- Multiple Type Parameters)
It doesn't have to be K and V.
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Speaker 1 (10- Multiple Type Parameters)
Now we replace the T with the K and
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Speaker 1 (10- Multiple Type Parameters)
the int with the V.
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Speaker 1 (10- Multiple Type Parameters)
So back to our main method.
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Speaker 1 (10- Multiple Type Parameters)
Let's call utils
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print.
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Speaker 1 (10- Multiple Type Parameters)
Now look at the type of these parameters.
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Speaker 1 (10- Multiple Type Parameters)
Initially the Java compiler sees both these parameters as objects,
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Speaker 1 (10- Multiple Type Parameters)
but we can pass anything here.
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Speaker 1 (10- Multiple Type Parameters)
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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Speaker 1 (10- Multiple Type Parameters)
For the value we can pass a string,
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Speaker 1 (10- Multiple Type Parameters)
we can pass a number,
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Speaker 1 (10- Multiple Type Parameters)
we can pass anything.
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Speaker 1 (10- Multiple Type Parameters)
So let's run the program,
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Speaker 1 (10- Multiple Type Parameters)
we get 1 equals 10.
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Speaker 1 (10- Multiple Type Parameters)
Now we can also declare a class with multiple type parameters.
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Speaker 2 (10- Multiple Type Parameters)
So,
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Speaker 1 (10- Multiple Type Parameters)
here in this project,
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let's add a new class,
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Speaker 1 (10- Multiple Type Parameters)
we call it key value pair.
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Speaker 1 (10- Multiple Type Parameters)
Now here we add our type parameters,
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Speaker 1 (10- Multiple Type Parameters)
so k and v,
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Speaker 1 (10- Multiple Type Parameters)
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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Speaker 1 (10- Multiple Type Parameters)
Here we can add a constructor to initialize this,
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Speaker 1 (10- Multiple Type Parameters)
so public key value pair,
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Speaker 1 (10- Multiple Type Parameters)
we need two parameters here,
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Speaker 1 (10- Multiple Type Parameters)
key and value.
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Speaker 1 (10- Multiple Type Parameters)
And here we set this .key to key and
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this .value to value.
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Speaker 1 (10- Multiple Type Parameters)
So this is how we can declare multiple type parameters.
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