Question

public class A {
   protected ClassX a;
   public void foo() {
       operations on a;
   }
}

public class B extends A {
   private ClassY b; // ClassY extends ClassX
   @Override
   public void foo() {
       //wanna the exact same operation as A.foo(), but on b;
   } 
}

Sorry for such a not clear title.
My question is: in class B, when I call foo(), and I want the exact same operation as class A have on a. How do I achive that and without duplicate the same code from A?
If i leave out foo() in class B, would it work?
Or whats happening when I call super.foo() in foo();

Answer 1

Since ClassY extends ClassX, then you can remove private ClassY b from class B. Then you can just set your instance of ClassX to the a instance variable. This allows foo() to be inherited in class B, but still use the same logic and instance variable.

public class A {
    protected ClassX a

    public void foo() {
        // operations on a;
    }
}

public class B extends A {
    // do something to set an instance of ClassY to a; for example...
    public void setClassY(ClassY b){
        this.a = b;
    }
}