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

No. The compiler can't know what type jerry.callFriend("spike") would return. Also, your implementation just hides the cast in the method without any additional type safety. Consider this:

jerry.addFriend("quaker", new Duck());
jerry.callFriend("quaker", /* unused */ new Dog()); // dies with illegal cast

In this specific case, creating an abstract talk() method and overriding it appropriately in the subclasses would serve you much better:

Mouse jerry = new Mouse();
jerry.addFriend("spike", new Dog());
jerry.addFriend("quacker", new Duck());

jerry.callFriend("spike").talk();
jerry.callFriend("quacker").talk();