how to refer to an object with which func1 of class A is called when inside func2 of class B which is called using an object created in func1?

Question

I have a class A and within class AI have function func1 and func2 . In the same file I have class B and in that class BI have function func3 . In the main class, an object obj1 of class A is declared. With this object, func1 of class A is called. Within func1 of class A , an object obj2 of class B is created. With this object, func3 of class B is called. Now within func3 of class B , i want call func2 of class A with the object obj1 . For this I want to refer to that object from within func3 of class B . Is it possible? If yes, how?

I tried using this.this.func2 which wouldn't work. For now I am passing the object obj1 as an argument and it works fine. But I want to do the same without passing it because I want to use an array of objects and every time the object should differ

class A {
    int attr1, attr2;

    public void func1() {
        int attr1 = 3;
        int attr2 = 6;
        B obj2 = new B();
        obj2.func3();
    }

    public void func2() {
        this.attr1 = 5;
        this.attr2 = 10;
    }
}

class B {
    int atr1, atr2;

    public void func3() {
        atr1 = 4;
        atr2 = 8;
        // here I want to access the object obj1 to call the function func2()
    }
}

public class Main {
    public static void main(String args[]) {
        A obj1 = new A();
        A.func1();
    }
}

Answer 1

Is it possible?

Yes.

If yes, how?

Option 1: Pass as parameter

Pass obj1 as parameter to func3 .

Or more precisely, since func3 is called from a method of obj1 , pass this as the parameter value:

class A {
    public void func1()
    {
        B obj2 = new B();
        obj2.func3(this);
    }
}

class B {
    public void func3(A a)
    {
        a.func2();
    }
}

Option 2: Pass to constructor

Pass the A reference to the B constructor, and have B remember it in a field.

class A {
    public void func1()
    {
        B obj2 = new B(this);
        obj2.func3();
    }
}

class B {
    A a;
    public B(A a) {
        this.a = a;
    }
    public void func3()
    {
        this.a.func2();
    }
}

Option 3: Inner class

Make class B an inner class of A . Essentially the same as option 2, but the compiler handles the reference to A for you.

class A {
    public void func1()
    {
        B obj2 = new B();
        obj2.func3();
    }

    class B {
        public void func3()
        {
            A.this.func2();
        }
    }
}