Java Minutiae - Instantiating inner classes

Pop quiz - without reflection, access to private members, or changing the source, create an instance of Inner.

public final class Outer {
  public static final Outer INSTANCE = new Outer();
  private Outer() { }
  public class Inner { }
}

Note that Inner is non-static, so each Inner has a reference to its containing Outer.

Show Answer
Well it turns out that you can 'dereference' a containing instance to instantiate an inner class. The syntax is awkward, but it works: Inner inner = Outer.INSTANCE.new Inner();I've found this syntax most useful for testing package-scoped inner classes.