Inheritance and shadowing

[Sudhanshu Mishra]

Hi All,
I have a doubt regarding below code snippet

class A
{
	int a=9;
	public void display(){
		System.out.println(a);
	}
}
class B extends A{
	int a=10;
}
public class Inherit {
	public static void main(String...a)
	{
		B b=new B();
		b.display();
	}
}

OUTPUT : 9
Now if B extends A,it means that B also has method display().Also, B has a variable 'a' which is same as variable 'a' in parent class.Then why does it happen that we get the output as 9, even though B has inherited display() method and also it's own 'a' variable.
I know that instance variables are not overridden ,but I am really sorry I am unable to relate this fact with this problem.

I request to please be patient with me and give a reply.

Thanks...

[Dennis Grimbergen]

Sudhanshu Mishra wrote:
Now if B extends A,it means that B also has method display().

No it does not and that's why it prints 9.
You need to override the method in class B.

class B extends A{  
    int a=10;

    @Override
    public void display() {
        System.out.println(a); // <-- prints 10 now
    }
}

[Jeff Verdegan]

Sudhanshu Mishra wrote:Then why does it happen that we get the output as 9, even though B has inherited display() method

Because B doesn't have its own separate copy of that method. A's implementation of that method is invoked, and precisely because variables are not overridden the only "a" variable available to that method is A's "a".

[Jayesh A Lalwani]

Data members do not get overridden in Java, only functions. Try this

class A
{
	public void display(){
		System.out.println(getA());
	}
        public int getA() { return 9;}
}
class B extends A{
	int a=10;
        public int getA() { return 10;}
}
public class Inherit {
	public static void main(String...a)
	{
		B b=new B();
		b.display();
	}
}