生成全球唯一32位码

public class RandomGUIDUtil extends Object {

    public String valueBeforeMD5 = "";
    public String valueAfterMD5 = "";
    private static Random myRand;
    private static SecureRandom mySecureRand;

    private static String s_id;

    /*
     *  静态块初始化
     */

    static {
        mySecureRand = new SecureRandom();
        long secureInitializer = mySecureRand.nextLong();
        myRand = new Random(secureInitializer);
        try {
            s_id = InetAddress.getLocalHost().toString();
        } catch (UnknownHostException e) {
            System.out.println("构造带指定详细消息和嵌入异常!");
        }

    }

    public RandomGUIDUtil() throws Exception {
        getRandomGUID(false);
    }

    public RandomGUIDUtil(boolean secure) throws Exception {
        getRandomGUID(secure);
    }

    /*
     * 随机生成GUID
     */
    private void getRandomGUID(boolean secure) throws Exception {
        MessageDigest md5 = null;
        StringBuffer sbValueBeforeMD5 = new StringBuffer();

        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            logger.error("初始化MD5出错！");
            throw new NoSuchAlgorithmException("初始化MD5出错！");
        }

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

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

            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) {
            logger.error("获得MD5加密码出错!");
            throw new Exception("初始化MD5出错！");
        }
    }

    /**
     * 生成一个GUID串
     * @return GUID
     * @throws Exception
     */
    public static String newGuid() throws Exception{
        RandomGUIDUtil rdmGUID = new RandomGUIDUtil();
        return rdmGUID.toString();
    }

    /*
     * 生成以主机串号、显卡串号、主板号，以保证唯一性的32位编码
     */
    public String toString() {
        String raw = valueAfterMD5.toUpperCase();
        StringBuffer sb = new StringBuffer();
        sb.append(raw.substring(0, 8));
        sb.append(raw.substring(8, 12));
        sb.append(raw.substring(12, 16));
        sb.append(raw.substring(16, 20));
        sb.append(raw.substring(20));
        return sb.toString();
    }
}