can we execute the Overrided method of Base class with reference of type Super class?

[Tej Kumar Ch]

  class A{ 
	int i=9;
	   public void mA(){
		   System.out.println("A");
	   };
	}

	class B extends A { 
		int i=10;
	   public void mA(){ 
		   
		   System.out.println("In Mb");
	   }
	   public void mB() {
		   
		   System.out.println("In Mb");
	   }
	}

	class C extends B { 
	   public void mC(){
		   
		   System.out.println("In C");
	   }
	}
	
	public class TestClass{
		public static void main(String args []){
			
			
			A x = new B(); B y = new B(); B z = new C();
			
			((A)x).mA();
			x.mA();
			
			
			
		}
	}

OutPut for the above snippet is :

In B
In B

My doubt is

With the above I am expecting to invoke the Super class method and to print "A", But not happening.Its always calling the polymorphic method in B only.
Is there way to invoke that?

I tried with Casting but in vain

With Respect
Tej

[Henry Wong]

Tej Kumar Ch wrote:
With the above I am expecting to invoke the Super class method and to print "A", But not happening.Its always calling the polymorphic method in B only.
Is there way to invoke that?

With overridden methods, only the subclass can call the super class' version of the method -- and even then, the subclass can only call the super class version that was directly overridden.

Henry

[Tej Kumar Ch]

With overridden methods, only the subclass can call the super class' version of the method -- and even then, the subclass can only call the super class version that was directly overridden.

Hi Henry,

I am afraid , I didnt get your point, can you please elaborate.

With Respect
Tej

[Roel De Nijs]

Tej Kumar Ch wrote:With the above I am expecting to invoke the Super class method and to print "A", But not happening.Its always calling the polymorphic method in B only.
Is there way to invoke that?

Your understanding is wrong!

You have to remember 1 very important rule: Which instance methods you can call/invoke is determined at compile time based on the reference variable type. Which instance method is actually executed is decided at runtime based on the type of the actual object (= polymorphism). That's really a very, very important rule!

Now we go back to your example:

A x = new B();
((A)x).mA(); // line1
x.mA(); // line2

So if we apply the aforementioned rule to this code:
1/ the type of reference variable x is A => all methods defined in class A can be invoked
2/ the type of the actual object reference variable x is referring to, is B => the method mA in B (which overrides method mA in A) will be executed (printing In Mb).
3/ the type of reference variable x is A, the code on line1 doesn't make any difference and is completely equivalent to the code on line2. Because you cast, you are temporarely changing the type of the reference variable to A (but it was already A, so it doesn't make any difference). You do not change the type of the actual object the reference variable is referring to (which is required to execute another method)

So which options do you have to execute method mA in A?
1/ Make sure the actual object the reference variable is referring to is of type A

A a = new A();
a.mA();

2/ In the overridden method you can invoke the base class version of the method using the super keyword. So change the code of method mA in B to

public void mA() {
  super.mA();
  System.out.println("In Mb");
}

Now the code

A x = new B();
x.mA();

prints
A
In Mb

Hope it helps!
Kind regards,
Roel

[Tej Kumar Ch]

Hi Roel,

Thanks a lot for your elaborate and explanatory responses, it cleared my query

With Respect
Tej