What is the use of creating a class inside interface and interface inside class

Question

I want to know what is the need of placing a class inside interface and an interface inside class?

class A {    interface B {} }  interface D {    class E {} }  

Answer 1

This i am copying and pasting from some link (i earlier did and sharing with you) May be that can help you a bit.

1)

interface employee{ class Role{       public String rolename;       public int roleId;  } Role getRole(); // other methods  } 

In the above interface you are binding the Role type strongly to the employee interface(employee.Role). 2) With a static class inside an interface you have the possibility to shorten a common programming fragment: Checking if an object is an instance of an interface, and if so calling a method of this interface. Look at this example:

  public interface Printable {     void print();      public static class Caller {         public static void print(Object mightBePrintable) {                 if (mightBePrintable instanceof Printable) {                         ((Printable) mightBePrintable).print();                 }         }     } } 

Now instead of doing this:

  void genericPrintMethod(Object obj) {     if (obj instanceof Printable) {         ((Printable) obj).print();     } } 

You can write:

   void genericPrintMethod(Object obj) {          Printable.Caller.print(obj);     }