instanceOf??

[srikanth reddy]

hi frnds,

class Tree{}
class Pine extends Tree{}
class Oak extends Tree{}
public class Forest 
{  public static void main( String[] args ) 
   {  Tree tree = new Pine();
 
      if( tree instanceof Pine )
      System.out.println( "Pine" );
 
      if( tree instanceof Tree )
      System.out.println( "Tree" );
 
      if( tree instanceof Oak )
      System.out.println( "Oak" );
 
      else System.out.println( "Oops" );
   }
}

This is a simple doubt .Here tree is of type Tree and it points to an object of pine .so in the output

tree is an instance of Pine ..that is fine ..
tree is not an instance of Oak ..that is also fine..
tree is of type Tree ...is it right to say that tree is an instance of Tree..

coz in the output i get..
pine
Tree
Oops

thanks

sri

[Sandeep Chhabra]

Hi,

Doubt is obvious. Ok Do you belive that every String is an Object Or Do you belive that every Chair or Table is a Furniture...??

If you DO then why, simply because
String extends Object
and ofcourse Chair is a Furniture (we can say Chair extends Furniture)

If we say that String is an object or Chair is a Furniture that means we say that String is an instance of Object or Chair is an instance of Furniture.

Similary every Pine is also instance of Tree
you will get the same result if you try
Pine isntanceof Object.......would'nt you?

Hence every subclass Object is ofcourse an instance of its super class

Hope it helps
[ October 11, 2005: Message edited by: Sandeep Chhabra ]