How do I convert a byte array to hex?
Author: Deron Eriksson
Description: This Java tutorial describes how to convert a byte array to hex.
Tutorial created using: Windows XP || JDK 1.5.0_09 || Eclipse Web Tools Platform 2.0 (Eclipse 3.3.0)

The ByteArrayToHexExample class demonstrates two methods for converting a byte array to its hex equivalent. The first method uses Hex.encodeHex() from the ApacheSW CommonsSW Codec library. The second method uses standard JavaSW to iterate over the byte array, converting each byte to its hex string equivalent.

package test;


import org.apache.commons.codec.binary.Hex;

public class ByteArrayToHexExample {

	public static void main(String[] args) throws NoSuchAlgorithmException, FileNotFoundException, IOException {

		String file = "";
		MessageDigest md = MessageDigest.getInstance("MD5");
		byte[] digest = getDigest(new FileInputStream(file), md, 2048);

		// method #1
		// convert byte array to hex string with apache commons codec
		String result = new String(Hex.encodeHex(digest));
		System.out.println("MD5 Digest (via commons codec):" + result);

		// method #2
		// convert byte array to hex string using no external libraries
		StringBuffer sb = new StringBuffer();
		for (byte b : digest) {
			sb.append(Integer.toHexString((int) (b & 0xff)));
		System.out.println("MD5 Digest (without external libraries):" + sb.toString());


	public static byte[] getDigest(InputStream is, MessageDigest md, int byteArraySize)
			throws NoSuchAlgorithmException, IOException {

		byte[] bytes = new byte[byteArraySize];
		int numBytes;
		while ((numBytes = != -1) {
			md.update(bytes, 0, numBytes);
		byte[] digest = md.digest();
		return digest;


The result of executing ByteArrayToHexExample is shown below. As you can see, both techniques generate the same hex results.

MD5 Digest (via commons codec):301d61853fc9ce94bbfb55b56c218d06
MD5 Digest (without external libraries):301d61853fc9ce94bbfb55b56c218d6