F-bounded style

f-bounded.java

/**
* If the return type must be the type of the class that implements the interface, 
* then what you want is called an F-bounded type
*/
public interface A<T extends A<T>> {
  public T b();
}

public class C implements A<C> {
  public C b() { ... }
}

public class D implements A<D> {
  public D b() { ... }
}