CODEWITHSUNDEEP
javagenericsfunctional-interface
Hatefiend
Hatefiend

Reputation: 3596

Generic function as functional interface?

I have the following function which returns an List of the same type as which it is passed.

<T> List<T> foo(T bar)
{
    ...
}

I want to have this same function, except in the form of a Java Functional Interface. I've tried the following:

final <T> Function<T, List<T>> foo;

But it does not like the <T>. If I omit <T> like:

final Function<T, List<T>> foo;

It claims it cannot find type T, exactly the same error as if I were to define the original function as:

List<T> foo(T bar) // cannot find type 'T'
{
    ...
}

I want to have function foo as a first class function.

Upvotes: 0

Views: 70

Answers (1)

Bohemian
Bohemian

Reputation: 425003

You’re confusing a method with a class, which may be implemented as a lambda.

If T isn’t a type in the context of the code, you can’t type anything.

You can do this:

class MyClass<T> implements Function<T, List<T>> {
    public List<T> accept(T t) {
         // some impl
    }
}

Upvotes: 3

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