Getting hold of the outer class object from the inner class object

Question

I have the following code. I want to get hold of the outer class object using which I created the inner class object inner. How can I do it?

public class OuterClass {      public class InnerClass {         private String name = "Peakit";     }      public static void main(String[] args) {         OuterClass outer = new OuterClass();         InnerClass inner = outer.new InnerClass();        // How to get the same outer object which created the inner object back?         OuterClass anotherOuter = ?? ;          if(anotherOuter == outer) {              System.out.println("Was able to reach out to the outer object via inner !!");         } else {              System.out.println("No luck :-( ");         }     } } 

EDIT: Well, some of you guys suggested of modifying the inner class by adding a method:

public OuterClass outer() {    return OuterClass.this; } 

But what if I don't have control to modify the inner class, then (just to confirm) do we have some other way of getting the corresponding outer class object from the inner class object?

Answer 1

Within the inner class itself, you can use OuterClass.this. This expression, which allows to refer to any lexically enclosing instance, is described in the JLS as Qualified this.

I don't think there's a way to get the instance from outside the code of the inner class though. Of course, you can always introduce your own property:

public OuterClass getOuter() {     return OuterClass.this; } 

EDIT: By experimentation, it looks like the field holding the reference to the outer class has package level access - at least with the JDK I'm using.

EDIT: The name used (this$0) is actually valid in Java, although the JLS discourages its use:

The $ character should be used only in mechanically generated source code or, rarely, to access pre-existing names on legacy systems.