Question

I have an inner class (non-static) which is using a reference to an enclosing class in its initialization. Will the inner class keep a reference to the enclosing class now?

class Enclosing {
  class Inner {
    private final ABC innerField = outerField.computeSomething();
  }

  private final XYZ outerField = something();
}

UPDATE

I am very much aware that one can reference the outer class with Enclosing.this.

But, if the class doesn’t use the reference, must the reference be there after compilation? Is it necessary even if the reference is only used in the initialization?

Where does it say that an inner class always holds a reference to the outer class?

Answer 1

A non-static nested class always holds a reference to the enclosing class. In your example, you can reference the enclosing class from Inner as Enclosing.this.

JLS 8.1.3 “Inner classes and Enclosing Instances”:

“An instance i of a direct inner class C of a class O is associated with an instance of O, known as the immediately enclosing instance of i. The immediately enclosing instance of an object, if any, is determined when the object is created (§15.9.2).”