Overriding a super class's instance variables

Question

Why are we not able to override an instance variable of a super class in a subclass?

Answer 1

Do you mean with overriding you want to change the datatype for example?

What do you do with this expression

public class A {
   protected int mIndex;

   public void counter(){
      mIndex++;
   }

}

public class B extends A {
   protected String mIndex; // Or what you mean with overloading
}

How do you want to change the mIndex++ expression without operator overloading or something like this.