内部类的静态初始化程序？

Question

How to allow static initializer on a inner class like this:

public class MyClass {

    public class InnerClass {
        static {
            // do something
        }
        public bar(){
            // do something
        }
    }

    // method stuff
    public void foo() {
        // do something
    }

} 

Answer 1

From JLS 8.1.3 Inner Classes and Enclosing Instances :

Inner classes may not declare static initializers (§8.7) or member interfaces.

What you may want is a nested class:

public static class InnerClass { // note "static"

Answer 2

You need to define the InnerClass class as static. But, thereafter, it won't be a regular inner class.

Answer 3

As it's already stated by @yshavit you can't declare static initializers, but from what I found you can get around that by declaring a method to do any initializations you want and simply call it when defining your class' fields. For example I implemented this iterator (this is an anonymous inner class) :

public Iterator<String> iterator() {

    return new Iterator<String>() {

        int someField = initializeIterator();

        // Keeps current position in the list of direct neighboring out

        private int initializeIterator() {
            // Do your initializations 
        }

        @Override
        public boolean hasNext() {
            //hasNext implementation
        }

        @Override
        public Vertex next() { 
            //next implementation
         } 
         //...

This feels very hack-y and I wonder If I'm missing something but this totally works and the initialization method is only called once just like a static initialization block would be...