no enclosing instance of type… in scope

Question

I investigate java inner classes.

I wrote example:

public class Outer {
    public Outer(int a){}

    public class Inner {
        public Inner(Stri         


        

Answer 1

Inner is an inner class. It can only be created when there is an enclosing instance of the class containing the Inner class definition.

However, you've created a static nested class, Nested, which extends from this class. When you try to invoke the super constructor

public Nested(String str, Boolean b , Number nm)   { super("2",true);   }

it will fail because the super constructor, for Inner, depends on an instance of Outer, which doesn't exist in the static context of the Nested class. Jon Skeet provides a solution.

An explanation of the solution appears in the JLS here.

Superclass constructor invocations may be subdivided:

• Unqualified superclass constructor invocations begin with the keyword super (possibly prefaced with explicit type arguments).

• Qualified superclass constructor invocations begin with a Primary expression.

  • They allow a subclass constructor to explicitly specify the newly created object's immediately enclosing instance with respect to the direct superclass (§8.1.3). This may be necessary when the superclass is an inner class.