怎么用雪花算法生成唯一Id

您可以通过以下代码使用雪花算法生成唯一Id：

public class SnowFlake {
    private long workerId;
    private long datacenterId;
    private long sequence = 0L;
    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 SnowFlake(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException("workerId can't be greater than " + maxWorkerId + " or less than 0");
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than " + maxDatacenterId + " or less than 0");
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }
 
    public synchronized long nextId() {
        long timestamp = timeGen();
 
        if (timestamp < lastTimestamp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id for " + (lastTimestamp - timestamp) + " milliseconds");
        }
 
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            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 = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }
 
    protected long timeGen() {
        return System.currentTimeMillis();
    }
}

在代码中，workerId表示每台机器的唯一标识，datacenterId表示每个数据中心的唯一标识。可以根据自己的情况进行调整。调用nextId()方法即可生成雪花算法的唯一Id。