when to use nested class in java code example

Example 1: Nested classes in java

// anonymous inner class as method argument.
interface HelloWorld
{
   String print();
}
public class AnonymousInnerDemo
{
   // method accepts object of interface HelloWorld
   public void display(HelloWorld m)
   {
      System.out.println(m.print() + "example of anonymous inner class as method argument.");
   }
   public static void main(String[] args)
   {
      AnonymousInnerDemo obj = new AnonymousInnerDemo();
      // pass an anonymous inner class as an argument
      obj.display(new HelloWorld() {
         public String print() {
            return "Hi! ";
         }
      });
   }
}

Example 2: Nested classes in java

// Anonymous inner class in java
abstract class Anonymous
{
   public abstract void display();
}
public class AnonymousInnerExample
{
   public static void main(String[] args)
   {
      Anonymous obj = new Anonymous() {
         public void display() {
            System.out.println("anonymous inner class example");
         }
      };
      obj.display();
   }
}