nested class in java

1// example on inner class in java
2class OuterDemo
3{
4   int num;
5   // inner class
6   private class InnerDemo
7   {
8      public void display()
9      {
10         System.out.println("inner class");
11      }
12   }
13   // access inner class from method within
14   void printInner()
15   {
16      InnerDemo objInner = new InnerDemo();
17      objInner.display();
18   }
19}
20public class InnerClassExample
21{
22   public static void main(String[] args)
23   {
24      OuterDemo objOuter = new OuterDemo();
25      objOuter.printInner();
26   }
27}

1// example on static nested classes java
2import java.util.*;
3public class OuterClass
4{
5   static class NestedClass
6   {
7      public void display() 
8      {
9         System.out.println("static nested class example");
10      }
11   }
12   public static void main(String[] args) 
13   {
14      OuterClass.NestedClass nested = new OuterClass.NestedClass();	 
15      nested.display();
16   }
17}

1// example on method local inner class in java.
2class Outer
3{
4   // outer class instance method
5   void display()
6   {
7      int num = 96;
8      // method-local inner class
9      class MethodLocalInner
10      {
11         public void show()
12         {
13            System.out.println("in method local inner class " + num);
14         }
15      } // end of inner class
16      // access method local inner class
17      MethodLocalInner objInner = new MethodLocalInner();
18      objInner.show();
19   }
20   public static void main(String[] args)
21   {
22      Outer objOuter = new Outer();
23      objOuter.display();
24   }
25}

1// anonymous inner class as method argument.
2interface HelloWorld
3{
4   String print();
5}
6public class AnonymousInnerDemo
7{
8   // method accepts object of interface HelloWorld
9   public void display(HelloWorld m)
10   {
11      System.out.println(m.print() + "example of anonymous inner class as method argument.");
12   }
13   public static void main(String[] args)
14   {
15      AnonymousInnerDemo obj = new AnonymousInnerDemo();
16      // pass an anonymous inner class as an argument
17      obj.display(new HelloWorld() {
18         public String print() {
19            return "Hi! ";
20         }
21      });
22   }
23}

11. Can Outer class be static? --> No
22. Can inner class be static? --> Yes
33. Can you create an object from the inner class? --> Only if it's static
44. Can we have main method in inner class ? --> Only if it's static
55. Inner class can only be extended if it's static.

1OuterClass.InnerClass innerObject = outerObject.new InnerClass();
2