Binary Tree

/**
 * Write a description of class BinaryTree here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
public class BinaryTree
{
   // Root node pointer. Will be null for an empty tree.
  private Node root;

  /**
   Creates an empty binary tree -- a null root pointer.
  */
  public void BinaryTree() {
    root = null;
  }

  /**
   Returns true if the given target is in the binary tree.
   Uses a recursive helper.
  */
  public boolean lookup(int data) {
    return(lookup(root, data));
  }

  /**
   Recursive lookup  -- given a node, recur
   down searching for the given data.
  */
  private boolean lookup(Node node, int data) {
    if (node==null) {
      return(false);
    }

    if (data==node.data) {
      return(true);
    }
    else if (data      return(lookup(node.left, data));
    }
    else {
      return(lookup(node.right, data));
    }
  }

  /**
   Inserts the given data into the binary tree.
   Uses a recursive helper.
  */
  public void insert(int data) {
    root = insert(root, data);
  }

   /**
   Recursive insert -- given a node pointer, recur down and
   insert the given data into the tree. Returns the new
   node pointer (the standard way to communicate
   a changed pointer back to the caller).
  */
  private Node insert(Node node, int data) {
    if (node==null) {
      node = new Node(data);
    }
    else {
      if (data <= node.data) {
        node.left = insert(node.left, data);
      }
      else {
        node.right = insert(node.right, data);
      }
    }

    return(node); // in any case, return the new pointer to the caller
  }

  private class Node
  {
   int data;
   Node left;
   Node right;


   Node(int newData) {
      left = null;
      right = null;
      data = newData;
   }
  }
}

Source: http://cslibrary.stanford.edu/110/BinaryTrees.html