生成Id

public class IdWorker {

private long workerId;
private long datacenterId;
private long sequence;

public IdWorker(long workerId, long datacenterId, long sequence) {
    // sanity check for workerId
    if (workerId > maxWorkerId || workerId < 0) {
        throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
    }
    if (datacenterId > maxDatacenterId || datacenterId < 0) {
        throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
    }
    System.out.printf("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d",
            timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits,
            workerId);
    this.workerId = workerId;
    this.datacenterId = datacenterId;
    this.sequence = sequence;
}

private long twepoch = 1288834974657L;
private long workerIdBits = 5L;
private long datacenterIdBits = 5L;
private long maxWorkerId = -1L ^ (-1L << workerIdBits);
private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
private long sequenceBits = 12L;
private long workerIdShift = sequenceBits;
private long datacenterIdShift = sequenceBits + workerIdBits;
private long timestampLeftShift = sequenceBits + workerIdBits +
        datacenterIdBits;
private long sequenceMask = -1L ^ (-1L << sequenceBits);
private long lastTimestamp = -1L;

public long getWorkerId() {
    return workerId;
}

public long getDatacenterId() {
    return datacenterId;
}

public long getTimestamp() {
    return System.currentTimeMillis();
}

public synchronized long nextId() {
    long timestamp = timeGen();
    if (timestamp < lastTimestamp) {
        System.err.printf("clock is moving backwards. Rejecting requests until %d.", lastTimestamp);
        throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds",
                lastTimestamp - timestamp));
    }
    if (lastTimestamp == timestamp) {
        sequence = (sequence + 1) & sequenceMask;
        if (sequence == 0) {
            timestamp = tilNextMillis(lastTimestamp);
        }
    } else {
        sequence = 0;
    }
    lastTimestamp = timestamp;
    return ((timestamp - twepoch) << timestampLeftShift) |
            (datacenterId << datacenterIdShift) |
            (workerId << workerIdShift) |
            sequence;
}

private long tilNextMillis(long lastTimestamp) {
    long timestamp = timeGen();
    while (timestamp <= lastTimestamp) {
        timestamp = timeGen();
    }
    return timestamp;
}

private long timeGen() {
    return System.currentTimeMillis();
}

//---------------测试---------------
public static void main(String[] args) {
    IdWorker worker = new IdWorker(1, 1, 1);
    for (int i = 0; i < 30; i++) {
        System.out.println(worker.nextId());
    }
}

}