/*
This file contains the code for class EmptyNode which represents the
empty state of a 2-3-4 tree.  EmptyNode is an example of the
Null object pattern.

Since there is conceptually only one empty state for all the 2-3-4 trees,
EmptyNode is implemented with the Singleton pattern.

6/25/97

Copyright 1997,  Dung X. Nguyen - All Rights Reserved.

*/
class EmptyNode extends ANode234
{
  final public static EmptyNode Singleton = new EmptyNode ();

  final boolean isEmpty ()
  {
	  return true;
  }

  final Integer rootData ()
  {
	  return null;
  }

  final void insert (Tree234 parent, Integer n)
  {
      Node2 aNode2 = new Node2 (n);
  	   parent.changeRoot (aNode2);
  }

  final void insertHelper (Tree234 grandPo, Tree234 parent, Integer n)
  {
      insert (parent, n);
  }

  final void attach (Tree234 parent, Tree234 lTree, Integer n, Tree234 rTree)
  {
    //do nothing- should never be called.
  }

  final void drawRootAndSubtrees (int level)
  {
	   System.out.print ("{}");
  }
}