implementing an extended interface on a concrete class

Question

I don't know if this is a best practices or not. If I have a interface that extends another interface such as :

public interface A extends B{
    public void something();
};

and a concrete class that implements A such as:

public class MyClass implements A {
    @Override 
    public void something(){
        System.out.println("ZOINKS");
    }

    @Override
    public void somethingFromB(){
        System.out.println("Hey, Scoobs!");
    }
};

Should I be adding B to the concrete class to identify the other interface?

Answer 1

A extends B means "A is a B". By implementing A, MyClass says "I'm a A, and therefore I'm B".

So, given the Java semantic, it's perfectly right to only (directly) implement the specialized interface. It's clear, and it avoids redundancy.

The only case where a redefinition could be interesting is when you use an interface as a marker (which is probably not such a good idea). It's simpler to get the interfaces directly implemented by a class rather than all the interfaces, including the inherited and extended ones.

Personally, I never 'redeclare' an implementation.