Copied from the internet. And maybe the twepoch should be 1288834974657L.

SnowFlakeIdWorker.java

public class SnowFlakeIdWorker {
   
  private final long workerId;
  private final static long twepoch = 1390838400000L;
  private Long sequence = 0L;
  private final static long workerIdBits = 4L;
  public final static long maxWorkerId = -1L ^ -1L << workerIdBits;
  private final static long sequenceBits = 10L;
  private final static long workerIdShift = sequenceBits;
  private final static long timestampLeftShift = sequenceBits + workerIdBits;
  public final static long sequenceMask = -1L ^ -1L << sequenceBits;
  private long lastTimestamp = -1L;
   
  public SnowFlakeIdWorker(final long workerId) {
    super();
    if (workerId > this.maxWorkerId || workerId < 0) {
      throw new IllegalArgumentException(String.format(
      "worker Id can't be greater than %d or less than 0", this.maxWorkerId));
    }
    this.workerId = workerId;
  }
   
  public synchronized long nextId() {
    long timestamp = this.timeGen();
    if (this.lastTimestamp == timestamp) {
        this.sequence = (this.sequence + 1) & this.sequenceMask;
        if (this.sequence == 0) {
          System.out.println("###########" + sequenceMask);
          timestamp = this.tilNextMillis(this.lastTimestamp);
        }
    } else {
      this.sequence = 0L;
    }
    if (timestamp < this.lastTimestamp) {
      try {
        throw new Exception(
          String.format(
          "Clock moved backwards.  Refusing to generate id for %d milliseconds",
          this.lastTimestamp - timestamp));
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
    this.lastTimestamp = timestamp;
    long nextId = ((timestamp - twepoch << timestampLeftShift))
                  | (this.workerId << this.workerIdShift) | (this.sequence);
    return nextId;
  }
   
  private long tilNextMillis(final long lastTimestamp) {
    long timestamp = this.timeGen();
    while (timestamp <= lastTimestamp) {
      timestamp = this.timeGen();
    }
    return timestamp;
  }
   
  private long timeGen() {
    return System.currentTimeMillis();
  }
}