///// STUDENT TO FILL OUT ALL THE STUB METHODS IN THIS CLASS.

package tree234;
/**
* 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.
* @author  Dung X. Nguyen - Copyright 2000 - All Rights Reserved.
*/
class EmptyNode extends ANode234
{
   final public static EmptyNode Singleton = new EmptyNode ();

   private EmptyNode ()
   {
   }

   /**
   * Inserts an Integer into the owner tree without duplication.
   * This is the EmptyNode.  So just asks the owner to change its state to a Node2.
   * @param n != null.
   * @param owner the owner of this EmptyNode.
   */
   final void insert (Integer n, Tree234 owner)
   {
//// STUDENT TO WRITE CODE.
   }

	/**
   * Helps the owner's parent tree insert data, using the other two owner's siblings if necessary.
   * This is the EmptyNode.  So it is up to the other owner's siblings to decide what to do.
   * Hands one sibling to the other sibling and asks it to help owner's parent insert data.
   * @param ownerParent the parent of owner.
   * @param ownerSib1 one of the two siblings of owner.
   * @param ownerSib2 the sibling of sib1 and owner.
   * @param n an Integer to be properly inserted into ownerParent.
   * @param owner the owner of this EmptyNode
   */
	void helpParentInsert(Tree234 ownerParent, Tree234 ownerSib1, Tree234 ownerSib2, Integer n, Tree234 owner)
	{
//// STUDENT TO WRITE CODE.
	}

	/**
   * Helps the owner's parent insert data, using the one remaining owner's sibling if necessary.
   * This is the EmptyNode.  So it is up to the given owner's remaining sibling to decide what to do.
   * Asks the owner's remaining sibling to help the owner's parent insert data.
   * @param ownerParent the parent of owner.
   * @param sib one of the two sibblings of owner.
   * @param n an Integer to be properly inserted into ownerParent.
   * @param owner the owner of this EmptyNode
    */
	final void helpParentInsert(Tree234 ownerParent, Tree234 ownerSib, Integer n, Tree234 owner)
	{
//// STUDENT TO WRITE CODE.
	}

	/**
   * Helps the owner's parent insert data with the knowledge that all the owner's siblings are empty.
   * This is the EmptyNode.  Thus the owner's parent is a leaf.
   * Asks the owner's parent to insert data as a leaf.
   * @param ownerParent the parent of owner.
   * @param n an Integer to be properly inserted into ownerParent.
   * @param owner the owner of this EmptyNode
   */
	final void helpParentInsert (Tree234 ownerParent, Integer n, Tree234 owner)
	{
//// STUDENT TO WRITE CODE.
	}

   /**
   * Inserts data into owner when this EmptyNode is a leaf node.
   * Throws an IllegalStateException since the EmptyNode cannot be a leaf node.
   * @param n an Integer to be properly inserted into owner.
   * @param owner the owner of this EmptyNode
   */
	final void insertAsLeaf(Integer n, Tree234 owner)
	{
      throw new IllegalStateException ("Empty tree cannot be a leaf!");
	}

   /**
   * Inserts data into the owner when this EmptyNode is NOT a leaf node.
   * @param n an Integer to be properly inserted into owner.
   * @param owner the owner of this EmptyNode
   */
	final void insertNotAsLeaf(Integer n, Tree234 owner)
	{
//// STUDENT TO WRITE CODE.
	}

  /**
   * The owner of this EmptyNode is is a subtree of a given parent tree.
   * This is the EmptyNode, so there is no need to split the node.
   * Simply insert n into the owner tree.
   * @param ownerParent the parent of this tree.
   * @param n an Integer to be properly inserted into owner.
   * @param owner the owner of this EmptyNode
   */
   final void insertAsChild (Tree234 ownerParent, Integer n, Tree234 owner)
   {
      insert (n, owner); // short cut for owner.insert (n);
   }

   /**
   * Attaches the 3 components a 2-node to the owner tree in the proper order.
   * Throws an IllegalStateException since the owner is an empty tree and
   * cannot be the parent of any tree.
   * @param lTree a 2-3-4 tree whose elements are less than n.
   * @param n a data element.
   * @param rTree a 2-3-4 tree whose elements are greater than n.
   * @param owner the owner of this EmptyNode, must be the parent of a Tree234.
   */
   final void attach (Tree234 lTree, Integer n, Tree234 rTree, Tree234 owner )
   {
      throw new IllegalStateException ("EmptyNode.attach (...) does not make sense!");
   }
}