Why make private inner class member public in Java?

Question

What is the reason of declaring a member of a private inner class public in Java if it still can't be accessed outside of containing class? Or can it?

public class DataStructure {     // ...      private class InnerEvenIterator {         // ...          public boolean hasNext() { // Why public?             // ...         }     } } 

Answer 1

If the InnerEvenIterator class does not extend any class or implement any interface, I think it is nonsense because no other class can access any instance of it.

However, if it extends or implements any other non private class or interface, it makes sense. An example:

interface EvenIterator {     public boolean hasNext(); }   public class DataStructure {     // ...      private class InnerEvenIterator implements EvenIterator{         // ...          public boolean hasNext() { // Why public?             // ...         }     }      InnerEvenIterator iterator;      public EvenIterator getIterator(){          return iterator;     }       } 

Answer 2

This method can be made public in order to indicate that it's semantically public, despite the fact that compiler doesn't enforce visibility rules in this particular case.

Imagine that during some refactoring you need to make this inner class top-level. If this method is private, how would you decide whether it should be made public, or some more restrictive modifier should be used? Declaring method as public tells reader the intentions of original author - this method shouldn't be considered an implementation detail.