二叉树方法和节点

Question

从下面的代码我想向LinkedBinaryTree类添加一个方法，该类返回树的高度，以及BTNode中执行大部分工作的另一个方法。首先，检查root是否为null。如果是，那么树显然是空的并返回0.如果它不为null，则返回root.height（）。

   import java.util.Iterator;


public class LinkedBinaryTree<T> implements BinaryTree<T>
{
   protected BTNode<T> root;

   //-----------------------------------------------------------------
   //  Creates an empty binary tree.
   //-----------------------------------------------------------------
   public LinkedBinaryTree()
   {
      root = null;
   }

   //-----------------------------------------------------------------
   //  Creates a binary tree with the specified element as its root.
   //-----------------------------------------------------------------
   public LinkedBinaryTree (T element)
   {
      root = new BTNode<T>(element);
   }

   //-----------------------------------------------------------------
   //  Creates a binary tree with the two specified subtrees.
   //-----------------------------------------------------------------
   public LinkedBinaryTree (T element, LinkedBinaryTree<T> left,
      LinkedBinaryTree<T> right)
   {
      root = new BTNode<T>(element);
      root.setLeft(left.root);
      root.setRight(right.root);
   }

   //-----------------------------------------------------------------
   //  Returns the element stored in the root of the tree. Throws an
   //  EmptyCollectionException if the tree is empty.
   //-----------------------------------------------------------------
   public T getRootElement()
   {
      if (root == null)
         throw new EmptyCollectionException ("Get root operation "
            + "failed. The tree is empty.");

      return root.getElement();
   }

   //-----------------------------------------------------------------
   //  Returns the left subtree of the root of this tree.
   //-----------------------------------------------------------------
   public LinkedBinaryTree<T> getLeft()
   {
      if (root == null)
         throw new EmptyCollectionException ("Get left operation "
            + "failed. The tree is empty.");

      LinkedBinaryTree<T> result = new LinkedBinaryTree<T>();
      result.root = root.getLeft();

      return result;
   }

   //-----------------------------------------------------------------
   //  Returns the element in this binary tree that matches the
   //  specified target. Throws a ElementNotFoundException if the
   //  target is not found.
   //-----------------------------------------------------------------
   public T find (T target)
   {
      BTNode<T> node = null;

      if (root != null)
         node = root.find(target);

      if (node == null)
         throw new ElementNotFoundException("Find operation failed. "
            + "No such element in tree.");

      return node.getElement();
   }

   //-----------------------------------------------------------------
   //  Returns the number of elements in this binary tree.
   //-----------------------------------------------------------------
   public int size()
   {
      int result = 0;

      if (root != null)
         result = root.count();

      return result;
   }



 public Iterator<T> iterator() {
        return new ArrayIterator<T>();
    }

}