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

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)。