For example you have Animal superclass and Cat subclass.Say your subclass has speak(); method.
class Animal{
public void walk(){
}
}
class Cat extends Animal{
@Override
public void walk(){
}
public void speak(){
}
public void main(String args[]){
Animal a=new Cat();
//a.speak(); Compile Error
// If you use speak method for "a" reference variable you should downcast. Like this:
((Cat)a).speak();
}
}