Assign a subclass of a Generic class to a super class of this class

Question

I have couple of supplied interfaces

public interface Finder,T extends Item> {
    public S find(S s, int a);
}

public interf         


        

Answer 1

public class SimpleFinder,T extends Item> implements Finder{
    public S find(S s, int a){
        Stack stack = ....;
        ...
        stack = s.getCopy();
        .....
        return (S) stack;
    }
}

should work. Keep in mind that stack must be a Stack and not S to match getCopy() return type. I would expect S type to be Ok, since it extends Stack, but implementing it this is the behavior that I'm observing.