Enforce method overload

Question

Looking at great example Polymorphism vs Overriding vs Overloading , consider this scenario:

abstract class Human {

  public void goPee() {
    println("drop pants");
  }
}

class Male extends Human {

  public void goPee() {
    super.goPee();
    println("stand up");
  }
}

class Female extends Human {
  public void goPee() {
    super.goPee();
    println("sit down");
  }
}

My questions:

Is it possible, on concrete classes level, to enforce using super.goPee() inside goPee() ? if so - how ?
Is it possible, on abstract class level, to know which concrete class had called super.goPee() ? Rationale for that is if I would need to call method let's say liftToiletSeat() somewhere on abstract class level.

Thank you.

you could argue that this is the childs class responsibility. If the child class just doesn't want any hassle, sure, call the parents class which should be enough for everyone. I would even go as far as saying your function shouldn't need anything more for it to be complete, but that is besides the point. Lets say another Human, `child` doesn't wear pants, so it has got its own way of peing. (just `println("make_a_mess");` I guess). (This class wouldn't want to call the parent. Or if it for some other reasons want to implement everything itself: why disallow that) — Nanne, May 29 '14 at 18:36

score 2 · Accepted Answer · answered May 29 '14 at 18:39

You can enforce it by not giving the subclass a choice, by using a simple Template Method Pattern. In the superclass that wants to enforce a call to super, don't give a choice.

Make the method final so it can't be overridden, and then call an abstract protected method that must be overridden. The superclass behavior is enforced.

abstract class Human {

   public final void goPee() {
       System.out.println("drop pants");
       toStandOrNotToStand();
   }

   protected abstract void toStandOrNotToStand();
}

Then the subclass can't override the superclass method, so it can't decide not to call super, but it must override the abstract method to be concrete.

class Male extends Human {
    @Override
    protected void toStandOrNotToStand() {
        println("stand up");
    }
}

And Female can be done similarly.

It is possible to know the concrete class with the getClass() method, but it doesn't make sense to do subclass-specific behavior in a superclass. You should be able to have liftToiletSeat in the Male subclass.

Enforce method overload

1 Answers1