Casting Doubt

[Gitesh Ramchandani]

class t{
public void start() {System.out.println("in super");}
}
 
 
class tt extends t{

public void start() {System.out.println("in SUB");}
 
public static void main(String[] args) {
((t)new tt()).start();

}
}

Output is: in SUB

Doubt: why the output is in SUB, even when I�m casting it to super class?
[ January 11, 2008: Message edited by: Gitesh Ramchandani ]

[Ulf Dittmer]

Please QuoteYourSources.

[Gitesh Ramchandani]

Source: Self Doubt

[Sudhakar Duraiswamy]

hi Gitesh ,

  
class mainClass{
String  className ="main Class" ;
 
public void check(){
System.out.println("Inside main");
}
}
 
class child extends mainClass{
String  className ="child Class" ;
 
public void check(){
System.out.println("Inside child");
}
 
public static void main(String Args[]){
mainClass mainclass = (mainClass)new child();
mainclass.check();//Since you have overridden a method ,
   //you have actually informed the JVM that you indeed want
//a different functionality to be carried out than the one available in 'main class'.
//That is the reason it executes the child class method 
 
System.out.println(" classname ="+mainclass.className);//prints 'main class' because the variables are not overriden
 
// following are the  ways for accessing Parent class methods  using 'super.check()' or by creating object of the 'main class' 
}
}

Inside child
classname =main Class

[gurpreet singh]

It is because the "start()" method is overriden in class tt. Remember, Invocation of instance methods are determined by the object referred to at runtime. So at runtime it is Class tt object.

If you use the syntax "((t)new tt()).variable", then it will invoke the variable of superclass and not that of subclass. Because the invocation of variables is determined at compile time and not at runtime.

[Gitesh Ramchandani]

Thanks Sudhakar.

I get it now that overriding method will be invoked and decided during runtime based on the object type, rather than the reference type.

[Dean Jones]

Is it becoz polymorphism only applies to instance methods?