public class BinarySearchTree {

private TreeNode root;

/** Create a default binary tree */

public BinarySearchTree() {

}

/** Create a binary tree from an array of objects */

public BinarySearchTree(Object[] objects) {

for (int i = 0; i < objects.length; i++)

insert(objects[i]);

}

/** Insert element o into the binary tree

* Return true if the element is inserted successfully */

public boolean insert(Object o) {

if (root == null)

root = new TreeNode(o); // Create a new root

else {

// Locate the parent node

TreeNode parent = null;

TreeNode current = root;

while (current != null)

if (((Comparable)o).compareTo(current.element) < 0) {

parent = current;

current = current.left;

}

else if (((Comparable)o).compareTo(current.element) > 0) {

parent = current;

current = current.right;

}

else

return false; // Duplicate node not inserted

// Create the new node and attach it to the parent node

if (((Comparable)o).compareTo(parent.element) < 0)

parent.left = new TreeNode(o);

else

parent.right = new TreeNode(o);

}

return true; // Element inserted

}

/** Inorder traversal */

public void inorder() {

inorder(root);

}

/** Inorder traversal from a subtree */

private void inorder(TreeNode root) {

if (root == null) return;

inorder(root.left);

System.out.print(root.element + " ");

inorder(root.right);

}

/** Postorder traversal */

public void postorder() {

postorder(root);

}

/** Postorder traversal from a subtree */

private void postorder(TreeNode root) {

if (root == null) return;

postorder(root.left);

postorder(root.right);

System.out.print(root.element + " ");

}

/** Preorder traversal */

public void preorder() {

preorder(root);

}

/** Preorder traversal from a subtree */

private void preorder(TreeNode root) {

if (root == null) return;

System.out.print(root.element + " ");

preorder(root.left);

preorder(root.right);

}

/** Inner class tree node */

private class TreeNode {

Object element;

TreeNode left;

TreeNode right;

public TreeNode(Object o) {

element = o;

}

}

}