// 
public final class DefaultKeyGenerator implements KeyGenerator {

 /**
     * 时间偏移量，从2016年11月1日零点开始
     */
 public static final long EPOCH;

 /**
     * 自增量占用比特
     */
 private static final long SEQUENCE_BITS = 12L;
 /**
     * 工作进程ID比特
     */
 private static final long WORKER_ID_BITS = 10L;
 /**
     * 自增量掩码（最大值）
     */
 private static final long SEQUENCE_MASK = (1 << SEQUENCE_BITS) - 1;
 /**
     * 工作进程ID左移比特数（位数）
     */
 private static final long WORKER_ID_LEFT_SHIFT_BITS = SEQUENCE_BITS;
 /**
     * 时间戳左移比特数（位数）
     */
 private static final long TIMESTAMP_LEFT_SHIFT_BITS = WORKER_ID_LEFT_SHIFT_BITS + WORKER_ID_BITS;
 /**
     * 工作进程ID最大值
     */
 private static final long WORKER_ID_MAX_VALUE = 1L << WORKER_ID_BITS;

 @Setter
 private static TimeService timeService = new TimeService();

 /**
     * 工作进程ID
     */
 private static long workerId;

 static {
 Calendar calendar = Calendar.getInstance();
        calendar.set(2016, Calendar.NOVEMBER, 1);
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        EPOCH = calendar.getTimeInMillis();
 }

 /**
     * 最后自增量
     */
 private long sequence;
 /**
     * 最后生成编号时间戳，单位：毫秒
     */
 private long lastTime;

 /**
     * 设置工作进程Id.
     * 
     * @param workerId 工作进程Id
     */
 public static void setWorkerId(final long workerId) {
 Preconditions.checkArgument(workerId >= 0L && workerId < WORKER_ID_MAX_VALUE);
 DefaultKeyGenerator.workerId = workerId;
 }

 /**
     * 生成Id.
     * 
     * @return 返回@{@link Long}类型的Id
     */
 @Override
 public synchronized Number generateKey() {
 // 保证当前时间大于最后时间。时间回退会导致产生重复id
 long currentMillis = timeService.getCurrentMillis();
 Preconditions.checkState(lastTime <= currentMillis, "Clock is moving backwards, last time is %d milliseconds, current time is %d milliseconds", lastTime, currentMillis);
 // 获取序列号
 if (lastTime == currentMillis) {
 if (0L == (sequence = ++sequence & SEQUENCE_MASK)) { // 当获得序号超过最大值时，归0，并去获得新的时间
                currentMillis = waitUntilNextTime(currentMillis);
 }
 } else {
            sequence = 0;
 }
 // 设置最后时间戳
        lastTime = currentMillis;
 if (log.isDebugEnabled()) {
            log.debug("{}-{}-{}", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").format(new Date(lastTime)), workerId, sequence);
 }
 // 生成编号
 return ((currentMillis - EPOCH) << TIMESTAMP_LEFT_SHIFT_BITS) | (workerId << WORKER_ID_LEFT_SHIFT_BITS) | sequence;
 }

 /**
     * 不停获得时间，直到大于最后时间
     *
     * @param lastTime 最后时间
     * @return 时间
     */
 private long waitUntilNextTime(final long lastTime) {
 long time = timeService.getCurrentMillis();
 while (time <= lastTime) {
            time = timeService.getCurrentMillis();
 }
 return time;
 }
}

// HostNameKeyGenerator.java
static void initWorkerId() {
   InetAddress address;
   Long workerId;
   try {
       address = InetAddress.getLocalHost();
   } catch (final UnknownHostException e) {
       throw new IllegalStateException("Cannot get LocalHost InetAddress, please check your network!");
   }
   String hostName = address.getHostName();
   try {
       workerId = Long.valueOf(hostName.replace(hostName.replaceAll("\d+$", ""), ""));
   } catch (final NumberFormatException e) {
       throw new IllegalArgumentException(String.format("Wrong hostname:%s, hostname must be end with number!", hostName));
   }
   DefaultKeyGenerator.setWorkerId(workerId);
}

// IPKeyGenerator.java
static void initWorkerId() {
   InetAddress address;
   try {
       address = InetAddress.getLocalHost();
   } catch (final UnknownHostException e) {
       throw new IllegalStateException("Cannot get LocalHost InetAddress, please check your network!");
   }
   byte[] ipAddressByteArray = address.getAddress();
   DefaultKeyGenerator.setWorkerId((long) (((ipAddressByteArray[ipAddressByteArray.length - 2] & 0B11) << Byte.SIZE)
           + (ipAddressByteArray[ipAddressByteArray.length - 1] & 0xFF)));
}

// IPSectionKeyGenerator.java
static void initWorkerId() {
   InetAddress address;
   try {
       address = InetAddress.getLocalHost();
   } catch (final UnknownHostException e) {
       throw new IllegalStateException("Cannot get LocalHost InetAddress, please check your network!");
   }
   byte[] ipAddressByteArray = address.getAddress();
   long workerId = 0L;
   // IPV4
   if (ipAddressByteArray.length == 4) {
       for (byte byteNum : ipAddressByteArray) {
           workerId += byteNum & 0xFF;
       }
   // IPV6
   } else if (ipAddressByteArray.length == 16) {
       for (byte byteNum : ipAddressByteArray) {
           workerId += byteNum & 0B111111;
       }
   } else {
       throw new IllegalStateException("Bad LocalHost InetAddress, please check your network!");
   }
   DefaultKeyGenerator.setWorkerId(workerId);
}