why do we use nested claases in java code example

Example 1: Nested classes in java

// example on method local inner class in java.
class Outer
{
   // outer class instance method
   void display()
   {
      int num = 96;
      // method-local inner class
      class MethodLocalInner
      {
         public void show()
         {
            System.out.println("in method local inner class " + num);
         }
      } // end of inner class
      // access method local inner class
      MethodLocalInner objInner = new MethodLocalInner();
      objInner.show();
   }
   public static void main(String[] args)
   {
      Outer objOuter = new Outer();
      objOuter.display();
   }
}

Example 2: 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! ";
         }
      });
   }
}