How to force derived class to call super method? (Like Android does)

Question

I was wondering, when creating new Activity classes and then overriding the onCreate() method, in eclipse I always get auto added: super.onCr

Answer 1

If you want to make absolutely sure that the superclass-method is called as well, you must trick a bit: Don't allow the superclass-method to be overwritten, but have it call an overridable protected method.

class Super
{
   public final void foo() {
      foo_stuff();
      impl_stuff();
   }

   protected void impl_stuff() {
      some_stuff_that_you_can_override();
   }
}

class Base extends Super
{
  protected void impl_stuff() { 
     my_own_idea_of_impl();
  }
}

That way, the user must call Super.foo() or Base.foo() and it will always be the base-class version as it was declared as final. The implementation-specific stuff is in impl_stuff(), which can be overriden.