CODEWITHSUNDEEP
java
user2693979
user2693979

Reputation: 2542

Why superclass invokes the subclass's overridden method?

I have two classes, Parent (superclass) and Child (subclass).

public class Parent(){

   public void hello(){
       System.out.println("HelloParent");
       bye();
   }

   public void bye(){
       System.out.println("ByeParent");
   }
}

public class Child extends Parent(){

   @Override
   public void hello(){
       super.hello();
   }

   @Override
   public void bye(){
       System.out.println("ByeChild");
   }
}

If I create a Child instance and invoke its hello() method, it invokes the Child's hello method, and not the Parent's hello method.

Child c = new Child();
c.hello();

Output:

"HelloParent"
"ByeChild"

But why is it not "ByeParent"?

Why doesn't it invoke the superclass's method?

Upvotes: 2

Views: 128

Answers (3)

Juned Ahsan
Juned Ahsan

Reputation: 68715

Any instance method call will happen on the object the instance belong to no matter where the code is. So while executing this code:

 public void hello(){
       System.out.println("HelloParent");
       bye();
   }

bye method will be called on the the calling object i.e. Child and hence Child method is called.

Upvotes: 2

jhocking
jhocking

Reputation: 5577

Overriding a method replaces it completely, it doesn't add on to it. If you also want to call the original method, you need to call it explicitly using the keyword "super":

@Override
public void bye(){
    super.bye();
    System.out.println("ByeChild");
}

Upvotes: 1

adarshr
adarshr

Reputation: 62583

Well, that is how polymorphism works in OO. Since the instance you are working with is Child, it is no surprise that Child.bye() was invoked!

If you really wanted it to print ByeParent, then you'd have to write the bye() in Child as follows:

@Override
public void bye(){
    super.bye();
    System.out.println("ByeChild");
}

Note that you could've also done this:

Parent obj = new Child();
obj.hello();

However, even in this case, it would still print ByeChild.

Upvotes: 1

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