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Program: Find height of a Binary Search Tree (BST)


For a binary tree to be a binary search tree (BST), the data of all the nodes in the left sub-tree of the root node should be less than or equals to the data of the root. The data of all the nodes in the right subtree of the root node should be greater than the data of the root. This example shows how to find height of a binary search tree.

Here is an example picture of binary search tree (BST):

Binary Search Tree

package com.java2novice.ds;

public class BstNode {

	private BstNode left;
	private BstNode right;
	private Integer data;

	public BstNode(Integer data) { = data;

	public BstNode getLeft() {
		return left;
	public void setLeft(BstNode left) {
		this.left = left;
	public BstNode getRight() {
		return right;
	public void setRight(BstNode right) {
		this.right = right;

	public Integer getData() {
		return data;

package com.java2novice.ds;

public class BinarySearchTreeImpl {

	private BstNode root;

	public boolean isEmpty() {

		return (this.root == null);

	public void insert(Integer data) {

		System.out.print("[input: "+data+"]");
		if(root == null) {
			this.root = new BstNode(data);
			System.out.println(" -> inserted: "+data);

		insertNode(this.root, data);
		System.out.print(" -> inserted: "+data);

	private BstNode insertNode(BstNode root, Integer data) {

		BstNode tmpNode = null;
		System.out.print(" ->"+root.getData());
		if(root.getData() >= data) {
			System.out.print(" [L]");
			if(root.getLeft() == null) {
				root.setLeft(new BstNode(data));
				return root.getLeft();
			} else {
				tmpNode = root.getLeft();
		} else {
			System.out.print(" [R]");
			if(root.getRight() == null) {
				root.setRight(new BstNode(data));
				return root.getRight();
			} else {
				tmpNode = root.getRight();

		return insertNode(tmpNode, data);

	public Integer findHeight(){

		return getNodeHeight(this.root);

	private Integer getNodeHeight(BstNode node) {

		if(node == null) {
			return -1;

		return Math.max(getNodeHeight(node.getLeft()), getNodeHeight(node.getRight()))+1;

	public static void main(String a[]) {

		BinarySearchTreeImpl bst = new BinarySearchTreeImpl();
		System.out.println("Height of the tree: "+bst.findHeight());

[input: 10] -> inserted: 10
[input: 20] ->10 [R] -> inserted: 20
[input: 21] ->10 [R] ->20 [R] -> inserted: 21
[input: 8] ->10 [L] -> inserted: 8
[input: 6] ->10 [L] ->8 [L] -> inserted: 6
[input: 16] ->10 [R] ->20 [L] -> inserted: 16
[input: 23] ->10 [R] ->20 [R] ->21 [R] -> inserted: 23
[input: 2] ->10 [L] ->8 [L] ->6 [L] -> inserted: 2
Height of the tree: 3
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Knowledge Centre
Class, Constructor and Primitive data types
Class is a template for multiple objects with similar features and it is a blue print for objects. It defines a type of object according to the data the object can hold and the operations the object can perform. Constructor is a special kind of method that determines how an object is initialized when created. Primitive data types are 8 types and they are: byte, short, int, long, float, double, boolean, char.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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