Reference variable casting

[Chetan Dodiya]

if

  class Animal{
   void doStuff(){}
}
 
class Dog extends Animal{
   void doStuff(){}
   public static void main(String[] args){
      Animal a=new Dog();
      a.doStuff();   //...1
      Dog d=(Dog)a;
      d.doStuff();   //...2
      ((Dog)a).doStuff();   //..3
   }
}  

at line 1 2 & 3 which methods are called means Dog's class And Animal's class???

[James Tharakan]

All those calls will invoke the method from the DOG class.

1.Because its overridden.
2.the object is actually a Dog class object and at this point the same object is actually refered by the Dog class reference
3.And again casting (for the time being)
[ November 14, 2008: Message edited by: James Tharakan ]

[Chetan Dodiya]

thank you very much....
[ November 14, 2008: Message edited by: Chetan dodiya ]

[marthi reddy]

Remember this rule, When a method is overridden(thru inheritance), then during run time, depending on the object type that the referrence variable is pointing to, the correspoding type's method will be invoked.

In the current example, ref variables a, d and the casted a(line 3) are all pointing to the Dog Object , doStuff() method is overridden and hence the doStuff() method in Dog Class will be invoked.