CODEWITHSUNDEEP
javapolymorphism
mtx
mtx

Reputation: 1234

Enforce method overload

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:

  1. Is it possible, on concrete classes level, to enforce using super.goPee() inside goPee() ? if so - how ?

  2. 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.

Upvotes: 0

Views: 59

Answers (1)

rgettman
rgettman

Reputation: 178263

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.

Upvotes: 2

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