Java : Inner Class , Nested Class , Static Class and Interfaces

Inner Class , Nested Class , Static Class and Interfaces

interface A {//All implementation in Interface = Static
    static class X{}            //To Avoid : if(X instance of A) ,can be accessed as A.X
    static abstract class Y{}    //Not valid - Cannot instantiate abstract class (static)
    static interface Z{}        //Not valid - Cannot instantiate Interface (static)
}

abstract class B {
    class X{}            //X=private by default
    abstract class Y{}    //
    interface Z{}        //
}

class C {
    void m(){class c{}}//Local inner class(visible only inside this method    )
    static class W{}    //Accessed as C.W
    class X{}            //Nested Class
    abstract class Y{}    // Implementing class needs
    interface Z{}
}

Nested Class:
1. Private by Default
2. Can access all the private members of super class
3.     C face=new C();
    C.X ear1=face.new X(); //logical grouping, readable and maintainable code
    C.X ear2=face.new X();
4. Same operation can also be done using external classes