利用JDK1.5中自带的Java.util生成GUID的方法! 均实践通过（Java）

<pre name="code" class="java">/** *UUID是1.5中新增的一个类，在java.util下，用它可以产生一个号称全球唯一的ID *author jpr1990 */</pre>

import java.util.UUID; public class Test { public static void main(String[] args) { UUID uuid = UUID.randomUUID(); System.out.println (uuid); } } import java.util.UUID; public class Test { public static void main(String[] args) { UUID uuid = UUID.randomUUID(); System.out.println (uuid); } }

关键代码：

UUID uuid = UUID.randomUUID(); System.out.println (uuid);

还有两种网上给出的生成方法:

import java.net.*; import java.util.*; import java.security.*; public class Guid extends Object { private String seedingString = ""; private String rawGUID = ""; private boolean bSecure = false; private static Random myRand; private static SecureRandom mySecureRand; private static String s_id; public static final int BeforeMD5 = 1; public static final int AfterMD5 = 2; public static final int FormatString = 3; 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 Guid() { } /* * 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 Guid(boolean secure) { bSecure = secure; } /* * Method to generate the random GUID */ private String 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)); seedingString = sbValueBeforeMD5.toString(); md5.update(seedingString.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)); } rawGUID = sb.toString(); } catch (Exception e) { System.out.println("Error:" + e); } return rawGUID; } public String createNewGuid(int nFormatType, boolean secure) { getRandomGUID(secure); String sGuid = ""; if (BeforeMD5 == nFormatType) { sGuid = this.seedingString; } else if (AfterMD5 == nFormatType) { sGuid = this.rawGUID; } else { sGuid = this.toString(); } return sGuid; } public String createNewGuid(int nFormatType) { return this.createNewGuid(nFormatType, this.bSecure); } /* * Convert to the standard format for GUID (Useful for SQL Server * UniqueIdentifiers, etc.) Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6 */ public String toString() { String raw = rawGUID.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(); } public static void main(String args[]) { for (int i=0;i<10;i++) { Guid guid=new Guid(); System.out.println("id===="+guid.getRandomGUID(true)); } } }

同样

//Java代码 UUID uuid = UUID.randomUUID(); System.out.println("{"+uuid.toString()+"}"); UUID uuid = UUID.randomUUID(); System.out.println("{"+uuid.toString()+"}");

说明：
UUID是指在一台机器上生成的数字，它保证对在同一时空中的所有机器都是唯一的。通常平台会提供生成UUID的API。UUID按照开放软件基金会(OSF)制定的标准计算，用到了以太网卡地址、纳秒级时间、芯片ID码和许多可能的数字。由以下几部分的组合：当前日期和时间(UUID的第一个部分与时间有关，如果你在生成一个UUID之后，过几秒又生成一个UUID，则第一个部分不同，其余相同)，时钟序列，全局唯一的IEEE机器识别号（如果有网卡，从网卡获得，没有网卡以其他方式获得），UUID的唯一缺陷在于生成的结果串会比较长。关于UUID这个标准使用最普遍的是微软的GUID(Globals Unique Identifiers)。