Java tutorial
//package com.java2s; //License from project: Apache License import java.util.Locale; public class Main { public static byte[] hexStringToBytes(String hexString) { if (hexString == null || hexString.equals("")) { return null; } hexString = hexString.toUpperCase(Locale.getDefault()); int length = hexString.length() / 2; char[] hexChars = hexString.toCharArray(); byte[] d = new byte[length]; for (int i = 0; i < length; i++) { int pos = i * 2; d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1])); } return d; } private static byte charToByte(char c) { return (byte) "0123456789ABCDEF".indexOf(c); } }