Why can outer Java classes access inner class private members?

java class private inner-classes private-members
Harish picture Harish · Nov 26, 2009 · Viewed 91.5k times · Source

I observed that Outer classes can access inner classes private instance variables. How is this possible? Here is a sample code demonstrating the same:

class ABC{
    class XYZ{
        private int x=10;
    }

    public static void main(String... args){
        ABC.XYZ xx = new ABC().new XYZ();
        System.out.println("Hello :: "+xx.x); ///Why is this allowed??
    }
}

Why is this behavior allowed?

Answer

Kaleb Brasee picture Kaleb Brasee · Nov 26, 2009

The inner class is just a way to cleanly separate some functionality that really belongs to the original outer class. They are intended to be used when you have 2 requirements:

  1. Some piece of functionality in your outer class would be most clear if it was implemented in a separate class.
  2. Even though it's in a separate class, the functionality is very closely tied to way that the outer class works.

Given these requirements, inner classes have full access to their outer class. Since they're basically a member of the outer class, it makes sense that they have access to methods and attributes of the outer class -- including privates.

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