Polymorphism by Java Example

public class SuperC {

    public void sayHello(){
        System.out.println("Hello Super");
    }
   
    public void sayBye(){
        System.out.println("Hello Super");
    }
   
    public static void main(String arg[]){
        SuperC sup1 = new SuperC();
        SuperC sub1 = new SubC();
       
        sup1 = sub1; // super class reference pointing to sub-class object
        sup1.sayHello(); // Hello Sub
       
        SuperC sup11 = new SuperC();
        SuperC sub11 = new SubC();
   
        sub11 = sup11; // Super class reference type to super-class object
        sub11.sayHello(); // Hello Super
       
        SuperC sup2 = new SuperC();
        SubC sub2 = new SubC();
       
        sup2 = sub2;  // super class reference pointing to sub-class object
        sup2.sayHello(); //Hello Sub
//       
        SuperC sup3 = new SuperC();
        SubC sub3 =  new SubC();
   
        sub3 = (SubC) sup3; // Exception in thread "main" java.lang.ClassCastException
                            // sub class reference type pointing to super class object
       
        SuperC sup4 = new SubC();
        SubC sub4 = new SubC();
       
        sub4 = (SubC) sup4  ; // Sub class reference pointer pointing to super class reference type
        sub4.sayHello(); // Hello Sub
    }
}

class SubC extends SuperC{

    public void sayHello(){
        System.out.println("Hello Sub");
    }
}