if am correctly undersatnd your query then ...
object can reside in parent's reference and vice versa is not true..
that is
public class A{
void run(){
System.out.println("its working by A");
}
}
class B extends A{
void run1(){
System.out.println("its working by B");
}
}
class TestDrive{
public static void main(
String args){
A a = new B();
a.run();
}
}
you may compile the above code and learn a lot of things by changing refrences ...