4. Static nested class

1. Types of Nested classes?

1. There are four kinds of nested class in Java.
1. static class: declared as a static member of another class
2. inner class: declared as an instance member of another class
3. local inner class: declared inside an instance method of another class
4. anonymous inner class: like a local inner class, but written as an expression which returns a one-off object

2. How to create an object for static nested classes?

1. By using outer class name, we can create object for static nested class.

class OuterClass {    ...   static  class InnerClass {        ...    } }

2. 
   

OuterClass.StaticInnerClass staticInnerClass = new OuterClass.StaticInnerClass();

3. We can’t create object for static nested class with outer class reference.

OuterClass outerClass = new OuterClass(); OuterClass.StaticInnerClass staticInnerClass2 = new outerClass.StaticInnerClass();

4. With in the Outer class we can directly create object without outer class name

OuterClass outerClass = new StaticInnerClass();

5. In static nested class we can define both static members and instance members.

package com.nested; public class OuterClass { int i = 1; static int j = 1; public void test() { //directly calling static members from outer class main(); new StaticInnerClass(); new OuterClass.StaticInnerClass(); //Print static member of static nested class System.out.println(StaticInnerClass.j); //Print instance member of static nested class System.out.println(new StaticInnerClass().i); } public static void main(){ System.out.println("static main"); } public static class StaticInnerClass { int i = 2; static int j = 2; } }

package com.nested; public class Main { public static void main(String[] args) { //Create an object for outer class OuterClass outerClass = new OuterClass(); //Create an object for StaticInnerClass class OuterClass.StaticInnerClass staticInnerClass = new OuterClass.StaticInnerClass(); System.out.println(staticInnerClass.i); System.out.println(OuterClass.StaticInnerClass.j); System.out.println(OuterClass.j); System.out.println(outerClass.i); } }