If I have a method in a subclass that asks for an object of the super class, how do i distinguish both?

Question

What I mean by this is, if I have A obj1 = new B(); A obj2 = new B(); A obj1 = new B(); A obj2 = new B(); I want to know how to call the same method for both objects, and also want to know how to know which object is calling the method and when:

For example, lets say my class hierarchy looks something like this:

abstract class A {
    public void method_1() {
        //Do something
    }
}

class B extends A {
    public boolean method_2(A obj) { 
        //Do something
    }
}

If I where to do obj1.method_2(obj2); How do I, inside method_2() , when I code it so both obj1 and obj2 call method_1() , distinguish which obj is calling the method?

I hope my question was clear enough. I'm sorry in advance if my English wasn't understandable enough.

Answer 1

obj1 which is instance of B but references class A, won't have access to method_2 So you need to cast like this

((B) obj1).method_2(obj2);

or you can change the reference to B instead of A

B obj1 = new B();

Base reference can't call the child's method.

Answer 2

public class Main {

    public static void main(String arg[] ) {
        A obj1 = new A() {};
        A obj2 = new B();
        B obj3 = new B();

        obj1.method_1("1 "+obj1.getClass());
        obj2.method_1("2 "+obj2.getClass());

        obj3.method_1("3 "+obj3.getClass());

        obj3.method_2(obj1);

        obj3.method_2(obj2);
    }

}


abstract class A {
    public void method_1(String className) {//Do something
        System.out.println("A.method_1() called by "+className);
    }
}


class B extends A {
    public boolean method_2(A obj) {//Do something
        super.method_1("4 "+obj.getClass());
        obj.method_1("5 "+obj.getClass());

        return true;
    }
}

Answer 3

You can NOT create an object of class A as its abstract class. However you can create object of B and pass it in place of A in method_2(). When you call method_1() inside method_2(), you are still calling it through object of class B. Here is the test program I could write based on my understanding of your question -

public class App {

    public static void main(String[] args) {

        B b = new B();
        B b2 = new B();
        b.method_2(b2); //Or
        //b.method_2((A)b2);

    }

}

abstract class A {
    public void method_1() {
        System.out.println("In method_1 = " + this.getClass());

    }
}

class B extends  A {
    public boolean method_2(A a) {
        System.out.println("In method_2 = " + this.getClass());
        a.method_1();
        return false;

    }
}

The result is that both methods are called by object of class B. You can user getSuperClass() method to get superclass name.