Anonymous Class.

[Abhi vijay]

The output of this program is :constructor of main class
Anonymous class.

How is the constructor getting invoked??? In this case, the new keyword is used for a different purpose, to create an anonymous class?

class Tptest
{
Tptest()
{
System.out.println("constructor of main class");
    }
  void go()
  {
    System.out.println("Main Class");
  }
}

public class Tp
{
  public static void main(String[] args)
  {
    Tptest p=new Tptest()
    {
 
      void go()
      {
        System.out.println("Anonymous Class");
      }
    };
    p.go();
  }
}

[Dave - added code tags]
[ October 12, 2008: Message edited by: David O'Meara ]

[Jeanne Boyarsky]

Abhi,
" Tptest p=new Tptest() {" - This code actually means to create an anonymous subclass of Tptest overriding the methods defined (in your case go.) Just as with a named subclass, the superclass constructor is automatically called.

[Campbell Ritchie]

The new keyword is used the same way it always is, to create an object (not a class).
What follows the new is whatever is supposed to be used to create the object, usually a constructor call. In this case you have a constructor call included in the anonymous class because you write new TpTest().

[What you write in the class body is whatever is overridden or implemented from the original class of that name-here TpTest.]

Of course you have a constructor; every class which has been compiled has a constructor; in the case of an anonymous class you can't write a constructor, so it uses the same constructor as its superclass. Yes, the original TpTest class is the superclass, and the anonymous class you have written is a subclass of TpTest, and the go() method is overridden.
You have a constructor in the TpTest superclass; when you create an anonymous class object, that constructor is invoked. Remember you always invoke a superclass constructor when you instantiate any subclass. Any "subclass" here means anything other than java.lang.Object.

It is a little like writing super(); at the beginning of a constructor.

[Abhi vijay]

Thanks a lot.

[Campbell Ritchie]

You're welcome Good to see we are being helpful.