gistfile1.java

// nested classes | static classes

public class Main {

    public static void main(String[] args) {

        Outer a = new Outer(6);
        Outer.InnerB b1 = a.new InnerB();
        Outer.InnerB b2 = new Outer(7).new InnerB();
        Outer.InnerC c1 = new Outer.InnerC(8);

        b1.printOuterValue();
        b2.printOuterValue();
        c1.printValue(); // as InnerC is static, we can never ref values of the parent
    }
}

class Outer {

    private int a;

    public Outer(int a) {
        this.a = a;
    }


    class InnerB {

        int b;

        public InnerB() {
            this.b = a; // works as we need to create new Outer before new Inner
        }

        public void printOuterValue() {
          // works as y is within our scope
            System.out.println(a);
        }
    }

    static class InnerC {
        private int c;

        public InnerC(int c) {
            this.c = c;
        }

        public void printValue() {
            System.out.println(c);
        }
    }
}