How do I make the method return type generic?

Question

Consider this example (typical in OOP books):

I have an Animal class, where each Animal can have many friends.
And subclasses like

Answer 1

There is another approach, you can narrow the return type when you override a method. In each subclass you would have to override callFriend to return that subclass. The cost would be the multiple declarations of callFriend, but you could isolate the common parts to a method called internally. This seems a lot simpler to me than the solutions mentioned above, and does not need an extra argument to determine the return type.