java实现雪花算法

public class SnowFlake {

    


    // 第二部分。设置一个时间初始值    2^41 - 1
    private long twepoch = 1585644268888L;

    // 第三部分。数据中心
    private final long dataCenterIdBits = 5L;
    private final long maxDataCenterId = -1L ^ (-1L << dataCenterIdBits);

    // 第四部分。机器id
    private final long workerIdBits = 5L;
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);

    // 第五部分。序号
    private final long sequenceBits = 12L;
    private final long sqeuenceMask = -1L ^ (-1L << sequenceBits);

    // 偏移量
    //工作id需要左移的位数，12位
    private long workerIdShift = sequenceBits;
    //数据id需要左移位数 12+5=17位
    private long dataCenterIdShift = sequenceBits + workerIdBits;
    //时间戳需要左移位数 12+5+5=22位
    private long timestampLeftShift = sequenceBits + workerIdBits + dataCenterIdBits;

    // 本地信息
    private long dataCenterId;
    private long workerId;
    private long sequence = 0L;
    private long lastTimestamp = -1L;


    public SnowFlake(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;
    }

    public synchronized long nextId() {
        long timestamp = System.currentTimeMillis();
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sqeuenceMask;
            
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }
        lastTimestamp = timestamp;
        
        return ((timestamp - twepoch) << timestampLeftShift) |
                (dataCenterId << dataCenterIdShift) |
                (workerId << workerIdShift) |
                sequence;
    }

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = System.currentTimeMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = System.currentTimeMillis();
        }
        return timestamp;
    }

    public static void main(String[] args) {
        SnowFlake snowFlake = new SnowFlake(1, 1);
        snowFlake.nextId();
    }

}