public class SnowflakeIdWorker {  
    // 起始的時間戳（自定義，例如系統(tǒng)上線時間）  
    private final long twepoch = 1288834974657L;  
  
    // 機器id所占的位數(shù)  
    private final long workerIdBits = 5L;  
  
    // 數(shù)據(jù)標(biāo)識id所占的位數(shù)  
    private final long datacenterIdBits = 5L;  
  
    // 最大機器ID  
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);  
  
    // 最大數(shù)據(jù)標(biāo)識ID  
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);  
  
    // 序列在id中占的位數(shù)  
    private final long sequenceBits = 12L;  
  
    // 機器ID左移12位  
    private final long workerIdShift = sequenceBits;  
  
    // 數(shù)據(jù)標(biāo)識id左移17位(12+5)  
    private final long datacenterIdShift = sequenceBits + workerIdBits;  
  
    // 時間截左移22位(5+5+12)  
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;  
  
    // 序列的掩碼，這里為4095 (0b111111111111=4095)  
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);  
  
    // 上次生成ID的時間截  
    private long lastTimestamp = -1L;  
  
    // 序列號  
    private long sequence = 0L;  
  
    // 工作機器ID  
    private final long workerId;  
  
    // 數(shù)據(jù)中心ID  
    private final long datacenterId;  
  
    public SnowflakeIdWorker(long workerId, long datacenterId) {  
        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));  
        }  
        this.workerId = workerId;  
        this.datacenterId = datacenterId;  
    }    
  
    // 生成ID  
    public synchronized long nextId() {  
        long timestamp = timeGen();  
  
        // 如果當(dāng)前時間小于上一次ID生成的時間戳，說明系統(tǒng)時鐘回退，拋出異常  
        if (timestamp < lastTimestamp) {  
            throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));  
        }  
  
        // 如果時間戳相同，則序列號自增  
        if (lastTimestamp == timestamp) {  
            sequence = (sequence + 1) & sequenceMask;  
            // 序列號溢出，等待下一毫秒  
            if (sequence == 0) {  
                timestamp = tilNextMillis(lastTimestamp);  
            }  
        } else {  
            // 時間戳改變，序列號重置為0  
            sequence = 0L;  
        }  
  
        // 更新最后的時間戳  
        lastTimestamp = timestamp;  
  
        // 移位并通過或運算拼到一起組成64位的ID  
        return ((timestamp - twepoch) << timestampLeftShift) |  
               (datacenterId << datacenterIdShift) |  
               (workerId << workerIdShift) |  
               sequence;  
    }  
  
    // 獲取當(dāng)前時間戳  
    protected long timeGen() {  
        return System.currentTimeMillis();  
    }  
  
    // 等待下一個毫秒  
    protected long tilNextMillis(long lastTimestamp) {  
        long timestamp = timeGen();  
        while (timestamp <= lastTimestamp) {  
            timestamp = timeGen();  
        }  
        return timestamp;  
    }

    public static void main(String[] args) {  
        SnowflakeIdWorker idWorker = new SnowflakeIdWorker(1, 1);  
        for (int i = 0; i < 5; i++) {  
            long id = idWorker.nextId();  
            System.out.println(Long.toBinaryString(id));  
            System.out.println(id);  
        }  
    }  
}