What would be the use of accepting itself as type arguments in generics

Question

I saw some code on an unrelated question but it got me curious as I never saw such construct with Java Generics. What would be the use of creating a generic class that can take

Answer 1

Without this, the parameter to the method foo could not be bound to type E.

If you have an implementation B of this abstract class, you can now enforce that method foo also requires its parameter to be of type B.

 class B extends A {
      void foo (B x){}
 }

Without that, foo would have to take any kind of A.

I agree that the syntax for this is less than elegant.