简单的UUID类

最近应工程的需要写了个简单的UUID类。

可通过方法 String getUUID(int length) 使用。length是制定返回字符串的长度。

一般最好能20位以上

package test;import java.net.InetAddress;import java.net.UnknownHostException;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.util.Random;public class UUIDGenerator {private static String baseUUID = null;private static long incrementingValue = 0;private static Random myRand = null;public static String getUUID(int length) {if (baseUUID == null) {getInitialUUID(length);}long i = ++incrementingValue;if (i >= Long.MAX_VALUE || i < 0) {incrementingValue = 0;i = 0;}return baseUUID;}protected static synchronized void getInitialUUID(int length) {if (baseUUID != null) {return;}if (myRand == null) {myRand = new Random();}long rand = myRand.nextLong();String sid;try {sid = InetAddress.getLocalHost().toString();} catch (UnknownHostException e) {sid = Thread.currentThread().getName();}StringBuffer sb = new StringBuffer();sb.append(sid);sb.append(":");sb.append(Long.toString(rand));sb.append(System.currentTimeMillis());MessageDigest md5 = null;try {md5 = MessageDigest.getInstance("MD5");} catch (NoSuchAlgorithmException e) {}md5.update(sb.toString().getBytes());byte[] array = md5.digest();StringBuffer sb2 = new StringBuffer();for (int j = 0; j < array.length; ++j) {int b = array[j] & 0xFF;sb2.append(Integer.toHexString(b));}int begin = 0;baseUUID = sb2.toString().substring(begin, length).toUpperCase();}public static void main(String[] args) {System.out.println(UUIDGenerator.getUUID(10));}}