import java.net.InetAddress; public class UUIDGenerator { /** * 产生一个32位的UUID * * @return */ public static String generate() { return new StringBuilder(32).append(format(getIP())).append( format(getJVM())).append(format(getHiTime())).append( format(getLoTime())).append(format(getCount())).toString(); } private static final int IP; static { int ipadd; try { ipadd = toInt(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); private final static String format(int intval) { String formatted = Integer.toHexString(intval); StringBuilder buf = new StringBuilder("00000000"); buf.replace(8 - formatted.length(), 8, formatted); return buf.toString(); } private final static String format(short shortval) { String formatted = Integer.toHexString(shortval); StringBuilder buf = new StringBuilder("0000"); buf.replace(4 - formatted.length(), 4, formatted); return buf.toString(); } private final static int getJVM() { return JVM; } private final static short getCount() { synchronized (UUIDGenerator.class) { if (counter < 0) { counter = 0; } return counter++; } } /** * Unique in a local network */ private final static int getIP() { return IP; } /** * Unique down to millisecond */ private final static short getHiTime() { return (short) (System.currentTimeMillis() >>> 32); } private final static int getLoTime() { return (int) System.currentTimeMillis(); } private final static int toInt(byte[] bytes) { int result = 0; for (int i = 0; i < 4; i++) { result = (result << 8) - Byte.MIN_VALUE + (int) bytes[i]; } return result; } }