java Hibernate UUID代码

package mypack;


import java.io.Serializable;  
import java.net.InetAddress;  
/** 
* 唯一主键生成办法。从Hibernate中提取出来。 
*/  
public class UUIDGenerator {  
 
private static final int IP;  
public static int IptoInt( byte[] bytes ) {  
 int result = 0;  
 for (int i=0; i<4; i++) {  
  result = ( result << 8 ) - Byte.MIN_VALUE + (int) bytes[i];  
 }  
 return result;  
}  
static {  
 int ipadd;  
 try {  
  ipadd = IptoInt( InetAddress.getLocalHost().getAddress() );  
 }  
 catch (Exception e) {  
  ipadd = 0;  
 }  
 IP = ipadd;  
}  
private static short counter = (short) 0;  
private static final int JVM = (int) ( System.currentTimeMillis() >>> 8 );  
 
public UUIDGenerator() {  
}  
 
/** 
 * Unique across JVMs on this machine (unless they load this class 
 * in the same quater second - very unlikely) 
 */  
protected int getJVM() {  
 return JVM;  
}  
 
/** 
 * Unique in a millisecond for this JVM instance (unless there 
 * are > Short.MAX_VALUE instances created in a millisecond) 
 */  
protected short getCount() {  
 synchronized(UUIDGenerator.class) {  
  if (counter<0) counter=0;  
  return counter++;  
 }  
}  
 
/** 
 * Unique in a local network 
 */  
protected int getIP() {  
 return IP;  
}  
 
/** 
 * Unique down to millisecond 
 */  
protected short getHiTime() {  
 return (short) ( System.currentTimeMillis() >>> 32 );  
}  
protected int getLoTime() {  
 return (int) System.currentTimeMillis();  
}  
  
private final static String sep = "";  
 
protected String format(int intval) {  
 String formatted = Integer.toHexString(intval);  
 StringBuffer buf = new StringBuffer("00000000");  
 buf.replace( 8-formatted.length(), 8, formatted );  
 return buf.toString();  
}  
 
protected String format(short shortval) {  
 String formatted = Integer.toHexString(shortval);  
 StringBuffer buf = new StringBuffer("0000");  
 buf.replace( 4-formatted.length(), 4, formatted );  
 return buf.toString();  
}  
 
public Serializable generate() {  
 return new StringBuffer(36)  
  .append( format( getIP() ) ).append(sep)  
  .append( format( getJVM() ) ).append(sep)  
  .append( format( getHiTime() ) ).append(sep)  
  .append( format( getLoTime() ) ).append(sep)  
  .append( format( getCount() ) )  
  .toString();  
}  
 
}  

public static void main(String args[]) throws Exception {
UUIDGenerator t=new UUIDGenerator();
System.out.println(t.generate().toString()); //4028be81421ea40a01421ea40aea0000
}