Java access the caller variable, is it possible? how?

Question

i have a class

    main {  
      Class1 class1=new Class1();  
      class1.function1(); 
    }


     class Class1 {   
        int abc=1;   
        ArrayList<Class2> class2s=new ArrayList<Class2>(); 

        int function1() {
          class2s.add(new Class2(asd));
          abc=555;   
        }    
     }

     class Class2 {   
        int functionx() {
          Log.e("abc?", ""+PARENT???.abc);   
        } 
     }

How can I get the caller Class's variable, say abc?

Answer 1

By making Class2 an inner, non-static class of Class1 :

class Class1 {   
    int abc=1;   
    ArrayList<Class2> class2s=new ArrayList<Class2>(); 

    int function1() {
      class2s.add(new Class2());
      abc=555;   
    }    

    class Class2 {   
        int functionx() {
            Log.e("abc?", abc);   
        } 
    }
}

Class2 will have a hidden reference to the instance of Class1.

Note Your example has one other mistake, in of that Class2 has no constructor. I have changed new Class2(asd) (which asd was also undefined) to new Class2()

Answer 2

You could pass the caller as an argument, like so:

int functionx(Class1 caller) {
  Log.e("abc?", ""+caller.abc)
}

and call it with

Class2 cls = new Class2()
cls.functionx(this)

As long as abc is visible to Class2. Otherwise there is no direct means of knowing your caller in Java. The variable class2s implements a uni-directional relationship between Class1 and Class2. So you can only navigate from Class1 to Class2, not the other way around.