Can anyone explain reason for this behaviour ?

[Gaurav Daga]

Hi All,

Have a look at following code:

class A{
public void a(A a){
System.out.println("Hi");
} 
}
class B extends A{
public void a(B b){
System.out.println("Hello ");
} 
}
public class OverloadingTest {
public static void main(String[] args) {
B b = new B();
A a = new B();
b.a(a);    
}
 
}

Output of this sample is 'Hi'.

Can anyone explain logic behind this behaviour?

I was expecting it to be 'Hello' as object passed was actually of Class B but reference holder was of Class A.

Cheers!!
Gaurav Daga

[Praveen Seluka]

Hi

The method a is overloaded and not overridden.
When you call b.a(a),it goes to class b and finds the a()ethod which is more appropriate.
out of two overloaded a()
that is 1. void a(A a) from class A
2. void a(B b) from class B

Void a(A a) is selected since reference of class a is sent as an argument.
When selecting overloaded method,jvm looks at the reference rather object.
Thats why it invoked method in class A and hence the output "Hi"

Thanks
Praveen SP

[Radu Zaharia]

Hi,

As you said in your class name, your example is about overloading, not overriding, so you cannot expect polymorphic behaviour. The method will be called based on the reference type, not the actual object type.

[Gaurav Daga]

Thanks both of you for your reply.

It means whenever method selection (for overloaded method), is to be done at that time JVM matches reference type of arguement not exact type of that object. Seems a bit strange to me. [:-(]

Anyways thanks for your prompt response.

~Gaurav Daga