Generic type argument in java generics

Question

Is there a way that I can pass a generic type to a generic class like

interface Wrapper<T, R> {}

interface Result<T, Wrapper<T, R>> {
    R getResult();
}

Here Result takes Wrapper one of the type with type arguments T and R. getResult method in Result interface returns R.

What I did is below,

interface Result<T, W> {
    <K> K getResult();
}

Is there a better way to do this in java.

Wrapper in interface Result<T, Wrapper<T, R> is not using your existing Wrapper<T, R> interface. It's hiding it by declaring a new type parameter of the same name. — ernest_k
– ernest_k, Commented Nov 21, 2019 at 6:00

Tagir Valeev · Accepted Answer · 2019-11-21 05:58:25Z

4

You need a separate type argument for a Result interface. Something like this:

interface Result<T, R, W extends Wrapper<T, R>> {
    R getResult();
}

Now you can use W inside the result to represent the Wrapper or T and R to represent wrapper components. It's possible though that W is completely unnecessary for you and having T and R is enough.

answered Nov 21, 2019 at 5:58

Tagir Valeev

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