Java Polymorphism

Question

This is a question just out of curiosity.

I know that when we call a subclass object's overridden method by the reference of it's superclass, JVM gives importance to the type of object and not to type of reference.

This is my simple code :

class Animal
{
    void eat()
    {
        System.out.println("Animal is eating...");
    }
}
class Horse extends Animal
{
    @Override
    void eat()
    {
        System.out.println("Horse is eating...");
    }
}
public class PolymorphismTest
{
    public static void main(String...args)
    {
        Animal a=new Animal();
        a.eat();

        Animal h= new Horse();
        h.eat();
    }
}

As expected, I get the output :

run:
Animal is eating...
Horse is eating...
BUILD SUCCESSFUL (total time: 0 seconds)

Now my question is , Is there any way that we can use reference h to call the superclass eat() method and not the subclass one? I know this is a question that is somewhat against the laws of polymorphism but you never know when the need may arise to do so.

I tried to typecast the reference h to Animal but no luck. Any ideas?

Possible duplicate of http://stackoverflow.com/questions/5411434/how-to-call-a-superclass-method-using-java-reflection — Akhi, Jun 11 '12 at 18:11
And also possible duplicate of http://stackoverflow.com/questions/1032847/can-java-call-parent-overridden-method-in-other-objects-but-not-subtype — Andrea Parodi, Jun 11 '12 at 18:13
I agree. Sorry for not going through it. I did some research but could not find this. — Kameron, Jun 11 '12 at 18:13

score 5 · Accepted Answer · answered Jun 11 '12 at 18:07

5

class Horse extends Animal
{
    @Override
    void eat()
    {
        super.eat();
    }
}

answered Jun 11 '12 at 18:07

Brett H

1,168
10
14

Yes, one shouldn't call the parent class' implementation in order to adhere to the laws of polymorphism. I will re-paste this link: http://stackoverflow.com/questions/1032847/can-java-call-parent-overridden-method-in-other-objects-but-not-subtype – Brett H Jun 12 '12 at 05:36

score 4 · Answer 2 · answered Jun 11 '12 at 18:08

4

No, you'll have to explicitly do so in the overridden method (i.e. super.eat()).

answered Jun 11 '12 at 18:08

user1329572

6,176
5
29
39

score 2 · Answer 3 · answered Jun 11 '12 at 18:09

2

You cannot do this by doing any form of typecasting. Your only way to call the method of the superclass is to either wrap it like Brett Holt showed, or you must have an object whose most specific runtime type is Animal.

answered Jun 11 '12 at 18:09

Jochen

2,277
15
22

Ashok M A · Answer 4 · 2016-06-16T12:05:29.253

2

In Java - All the methods are virtual methods that is most recent implementation is used while calling the function.

To answer your question, please make the method static in Animal class then you will get the eat method of Animal class called.

static void eat(){ 
      System.out.println("Animal is eating..."); 
}

edited Jun 16 '16 at 12:05

answered May 09 '13 at 11:01

Ashok M A

478
6
14

Java Polymorphism

4 Answers4

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