Java 基于雪花算法生成分布式id

public class SnowFlakeIdWorker {

    
    private static final long TW_EPOCH = 1622476800000L;

    
    private static final long WORKER_ID_BITS = 5L;

    
    private static final long DATA_CENTER_ID_BITS = 5L;

    
    private static final long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);

    
    private static final long MAX_DATA_CENTER_ID = ~(-1L << DATA_CENTER_ID_BITS);

    
    private static final long SEQUENCE_BITS = 12L;

    
    private static final long WORKER_ID_SHIFT = SEQUENCE_BITS;

    
    private static final long DATA_CENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;

    
    private static final long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATA_CENTER_ID_BITS;

    
    private static final long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);

    
    private final long workerId;

    
    private final long dataCenterId;

    
    private long sequence = 0L;

    
    private long lastTimestamp = -1L;

    
    public SnowFlakeIdWorker(long workerId) {
        // 计算最大值
        long maxMachineId = (MAX_DATA_CENTER_ID + 1) * (MAX_WORKER_ID + 1) - 1;

        if (workerId < 0 || workerId > maxMachineId) {
            throw new IllegalArgumentException(String.fORMat("Worker ID can't be greater than %d or less than 0", maxMachineId));
        }

        // 取高位部分作为机房ID部分
        this.dataCenterId = (workerId >> WORKER_ID_BITS) & MAX_DATA_CENTER_ID;
        // 取低位部分作为机器ID部分
        this.workerId = workerId & MAX_WORKER_ID;
    }

    
    public SnowFlakeIdWorker(long dataCenterId, long workerId) {
        if (workerId > MAX_WORKER_ID || workerId < 0) {
            throw new IllegalArgumentException(String.format("Worker ID can't be greater than %d or less than 0", MAX_WORKER_ID));
        }
        if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) {
            throw new IllegalArgumentException(String.format("DataCenter ID can't be greater than %d or less than 0", MAX_DATA_CENTER_ID));
        }

        this.workerId = workerId;
        this.dataCenterId = dataCenterId;
    }

    
    public synchronized long nextId() {
        long timestamp = timeGen();
        // 如果当前时间小于上一次 ID 生成的时间戳，说明发生时钟回拨，为保证ID不重复抛出异常。
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }

        if (lastTimestamp == timestamp) {
            // 同一时间生成的，则序号+1
            sequence = (sequence + 1) & SEQUENCE_MASK;
            // 毫秒内序列溢出：超过最大值
            if (sequence == 0) {
                // 阻塞到下一个毫秒，获得新的时间戳
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 时间戳改变，毫秒内序列重置
            sequence = 0L;
        }
        // 上次生成 ID 的时间戳
        lastTimestamp = timestamp;

        // 移位并通过或运算拼到一起
        return ((timestamp - TW_EPOCH) << TIMESTAMP_LEFT_SHIFT)
                | (dataCenterId << DATA_CENTER_ID_SHIFT)
                | (workerId << WORKER_ID_SHIFT)
                | sequence;
    }

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

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

// 初始化
SnowFlakeIdWorker idWorker = new SnowFlakeIdWorker(1, 0);

// 生成ID
for(int i=0; i<100; i++){
    System.out.println(idWorker.nextId());
}