package xxxxxxxxx

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

public class RandomGUID extends Object {

 public String valueBeforeMD5 = "";

 public String valueAfterMD5 = "";

 private static Random myRand;

 private static SecureRandom mySecureRand;

 private static String s_id;

 /*
  * Static block to take care of one time secureRandom seed. It takes a few
  * seconds to initialize SecureRandom. You might want to consider removing
  * this static block or replacing it with a "time since first loaded" seed
  * to reduce this time. This block will run only once per JVM instance.
  */

 static {
  mySecureRand = new SecureRandom();
  long secureInitializer = mySecureRand.nextLong();
  myRand = new Random(secureInitializer);
  try {
   s_id = InetAddress.getLocalHost().toString();
  } catch (UnknownHostException e) {
   e.printStackTrace();
  }

 }

 /*
  * Default constructor. With no specification of security option, this
  * constructor defaults to lower security, high performance.
  */
 public RandomGUID() {
  getRandomGUID(false);
 }

 /*
  * Constructor with security option. Setting secure true enables each random
  * number generated to be cryptographically strong. Secure false defaults to
  * the standard Random function seeded with a single cryptographically
  * strong random number.
  */
 public RandomGUID(boolean secure) {
  getRandomGUID(secure);
 }

 /*
  * Method to generate the random GUID
  */
 private void getRandomGUID(boolean secure) {
  MessageDigest md5 = null;
  StringBuffer sbValueBeforeMD5 = new StringBuffer();

  try {
   md5 = MessageDigest.getInstance("MD5");
  } catch (NoSuchAlgorithmException e) {
   System.out.println("Error:   " + e);
  }

  try {
   long time = System.currentTimeMillis();
   long rand = 0;

   if (secure) {
    rand = mySecureRand.nextLong();
   } else {
    rand = myRand.nextLong();
   }

   // This StringBuffer can be a long as you need; the MD5
   // hash will always return 128 bits. You can change
   // the seed to include anything you want here.
   // You could even stream a file through the MD5 making
   // the odds of guessing it at least as great as that
   // of guessing the contents of the file!
   sbValueBeforeMD5.append(s_id);
   sbValueBeforeMD5.append(":");
   sbValueBeforeMD5.append(Long.toString(time));
   sbValueBeforeMD5.append(":");
   sbValueBeforeMD5.append(Long.toString(rand));

   valueBeforeMD5 = sbValueBeforeMD5.toString();
   md5.update(valueBeforeMD5.getBytes());

   byte[] array = md5.digest();
   StringBuffer sb = new StringBuffer();
   for (int j = 0; j < array.length; ++j) {
    int b = array[j] & 0xFF;
    if (b < 0x10)
     sb.append(0);
    sb.append(Integer.toHexString(b));
   }

   valueAfterMD5 = sb.toString();

  } catch (Exception e) {
   System.out.println("Error:" + e);
  }
 }

 public String toString() {
  String raw = valueAfterMD5.toUpperCase();
  StringBuffer sb = new StringBuffer();
  sb.append(raw.substring(0, 8));
  sb.append("-");
  sb.append(raw.substring(8, 12));
  sb.append("-");
  sb.append(raw.substring(12, 16));
  sb.append("-");
  sb.append(raw.substring(16, 20));
  sb.append("-");
  sb.append(raw.substring(20));

  return sb.toString();
 }

 /*
  * Demonstraton and self test of class
  */
 public static void main(String args[]) {
  for (int i = 0; i < 100; i++) {
   RandomGUID myGUID = new RandomGUID();
   //System.out.println("Seeding   String=" + myGUID.valueBeforeMD5);
   //System.out.println("rawGUID=" + myGUID.valueAfterMD5);
   System.out.println("RandomGUID=" + myGUID.toString());
  }
 }
}