How to calculate the depth of a binary search tree

Question

I would like to calculate the summation of the depths of each node of a Binary Search Tree.

The individual depths of the elements are not already stored.

Answer 1

public int countNodes(Node root)
{  
   // Setup
   // assign to temps to avoid double call accessors. 
   Node left = root.getLeft();
   Node right = root.getRight();
   int count = 1; // count THIS node.

   // count subtrees
   if (left != null) count += countNodes(left);
   if (right != null) count += countNodes(right);

   return count;
}