Using static nested class as generic parameter

Question

I'm trying to create an interface with a bounded type parameter, with implementations supplying static nested classes to implement this parameter, as follows:

public interface InterfaceProblem<T extends IMyParameter>{
    T getParameterInstance();
}

interface IMyParameter {}

class MyClass implements InterfaceProblem<MyParameter> {
    public MyParameter getParameterInstance() {
        return new MyParameter();
    }

    class MyParameter implements IMyParameter{}
}

This gives me a compile error "MyParameter cannot be resolved to a type" on the MyClass declaration and its method. This disappears if I move the static class to its own type:

class MyClass implements InterfaceProblem<MyParameter> {
    public MyParameter getParameterInstance() {
        return new MyParameter();
    }
}

class MyParameter implements IMyParameter{}

However, I'd like to avoid that, since the MyParameter implementation is closely related to the MyClass implementation. Is there a better way I can acheive this? Is this correct compiler behaviour? (I'm using Eclipse Mars and Oracle jdk1.8.0_60)

'static inner' is a contradiction in terms. This is a static nested class. — user207421
– user207421, Commented Nov 7, 2015 at 9:14

Lukas Eder · Accepted Answer · 2015-11-07 09:06:17Z

1

You're missing an import:

import com.example.MyClass.MyParameter;

While the MyParameter type is on scope for the getParameterInstance() method's return type, it is not for the MyClass's binding of <T>

answered Nov 7, 2015 at 9:06

Lukas Eder

223k138 gold badges731 silver badges1.6k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Using static nested class as generic parameter

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related