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

I did the following in my lib kontraktor:

public class Actor {
    public SELF self() { return (SELF)_self; }
}

subclassing:

public class MyHttpAppSession extends Actor {
   ...
}

at least this works inside the current class and when having a strong typed reference. Multiple inheritance works, but gets really tricky then :)