public class Snowflake {
    // 開始時(shí)間戳，一般為項(xiàng)目啟動(dòng)時(shí)間
    private final long twepoch = 1288834974657L;
    // 機(jī)器ID所占的位數(shù)
    private final long workerIdBits = 5L;
    // 數(shù)據(jù)標(biāo)識(shí)ID所占的位數(shù)
    private final long datacenterIdBits = 5L;
    // 支持的最大機(jī)器ID，結(jié)果是31
    private final long maxWorkerId = ~(-1L << workerIdBits);
    // 支持的最大數(shù)據(jù)標(biāo)識(shí)ID，結(jié)果是31
    private final long maxDatacenterId = ~(-1L << datacenterIdBits);
    // 序列號(hào)所占的位數(shù)
    private final long sequenceBits = 12L;
    // 機(jī)器ID向左移12位
    private final long workerIdShift = sequenceBits;
    // 數(shù)據(jù)標(biāo)識(shí)ID向左移17位(12+5)
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    // 時(shí)間戳向左移22位(5+5+12)
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    // 生成序列的掩碼，這里是4095
    private final long sequenceMask = ~(-1L << sequenceBits);

    private long workerId; // 機(jī)器ID
    private long datacenterId; // 數(shù)據(jù)標(biāo)識(shí)ID
    private long sequence = 0L; // 序列號(hào)
    private long lastTimestamp = -1L; // 上次生成ID的時(shí)間戳

    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 = timeGen();

        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) & sequenceMask; // 序列號(hào)自增
            if (sequence == 0) { // 序列號(hào)超過最大值，則等待下一個(gè)時(shí)間戳
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L; // 序列號(hào)重置為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();
    }

    public static void main(String[] args) {
        Snowflake idWorker = new Snowflake(0, 0);
        for (int i = 0; i < 1000; i++) {
            long id = idWorker.nextId();
            System.out.println(Long.toBinaryString(id));
            System.out.println(id);
        }
    }
}

Snowflake snowflake = new Snowflake(workerId, datacenterId);
long id = snowflake.nextId();

UidGenerator uidGenerator = UidGenerator.getUidGenerator();
long id = uidGenerator.getUID();

SegmentIDGenImpl idGen = new SegmentIDGenImpl();
idGen.init();
long id = idGen.getId();

SnowFlake snowFlake = new SnowFlake(dataCenterId, machineId);
long id = snowFlake.nextId();

Snowflake snowflake = IdUtil.getSnowflake(1, 1);
long id = snowflake.nextId();