peakit peakit - 1 year ago 46
Java Question

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

I have the following code. I want to get hold of the outer class object using which I created the inner class object

. 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 = 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 Source

Within the inner class itself, you can use OuterClass.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.