A Working Binary Tree Class
If your BinaryTree class from Project 1 isn't up to being extended for
Project 2, BinaryTree.class contains
one you can use.  It has the following interface:
//Instance variables
protected BTNode root;
//Constructors
public BinaryTree()
public BinaryTree(Object item)
public BinaryTree(Object item, BinaryTree left, BinaryTree right)
//Instance methods
public Iterator iterator()
public Iterator inorderIterator()
public Iterator preorderIterator()
public Iterator postorderOterator()
//Inner classes 
protected BTNode
        //BTNode instance variables
        public Object value; 
	public BTNode left;  
       	public BTNode right; 
	 
         //BTNode constructors
        public BTNode()
        public BTNode(Object item)
        public BTNode(Object item, BTNode left, BTNode right)