Static member classes and instance variables.

Tip: Static member class doesn't have access to non static members of outer class.

Like always, let's test it with a small code snippet:

public class Dolls {

    public int dollCount = 25;

    public static class Barbie{

        void printVar () {

            System.out.println(dollCount);

        }

    }

    public static void main(String[] args) {

        Dolls.Barbie barbie = new Dolls.Barbie();

        barbie.printVar();

    }}

We have defined a top level class Dolls with static member class Barbie and member variable dollCount. Within Barbie we have used dollCount. 

If you try to run this example you will get a compilation error where dollCount is referenced within Barbie. 

Compilation error validates today's tip.