Overriding

[Nitin Menon]

Can anyone please help me to find the reason for the resultant output of the following code?

package overriding;

public class MethodOverriding {

	public static void main(String[] args) {
		Base base = new Child();
		
		base.show(" override..!");
		System.out.println("Value : "+base.value);
	}
}

class Base {
	String value = "Base";
	
	void show(String s){
		System.out.println("Base : "+s);
	}
}

class Child extends Base{
String value = "Child";
	
	void show(String s){
		System.out.println("Child : "+s);
	}
}

The output is:

Child :  override..!
Value : Base

I always thought the second output value would be

Value : Child

since the variable base points to the Child object.

Does anyone have an explanation please.

[Mark King]

Methods get overridden fields get shadowed, therefore methods depend on the object while fields depend on the reference type, since you declared the reference as Base, you get the value of the base field.

[S Majumder]

Completely agree with Mark .
Method overriding is done at compile and run time .Compiler will resolve which method to call and further resolved at runtime to the correct version of that method to call.Here at compile time compiler will call the show() and further at runtime it decides the Child version's of show() , because the actual object of type Child .But in the case of property the reference comes into the picture and the behavior is as expected !!!

Hope you understand .

Thanks ,
Satya

[Campbell Ritchie]

S Majumder wrote: . . .
Method overriding is done at compile and run time . . .

No, overriding is resolved at runtime. At compile time there is a check for which methods override each other, but the actual binding is not done until runtime.

[S Majumder]

At compile time there is a check for which methods override each other, but the actual binding is not done until runtime

I'm trying to explain this but in a different words ;)

Satya