Java利用時間戳生成三種唯一主鍵

/**
 * @Author: lgz
 * @Date: 2020/5/24 23:44
 */
public enum IdUtil {
    //有年月日的時間id
    DATE_TIME_ID {
        public long generateId() {
            return Long.parseLong(DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS")
                    .format(LocalDateTime.ofInstant(Instant.ofEpochMilli(super.generateId()), ZoneId.systemDefault())));
        }
    },
    //直接返回時間戳
    TIMESTAMP_ID {
        public long generateId() {
            return super.generateId();
        }
    },
    //時間戳左移10
    SHIFT_ID {
        public long generateId() {
            return super.generateId() << 10;
        }
    };


    //上一次的時間戳
    //在集羣環境中，可以使用redis存儲上一次時間
    private long lastTimestamp = -1L;

    //在集羣環境中，可以使用分佈式鎖
    private Lock lock = new ReentrantLock();

    private long nowTimestamp;

    public long generateId() {
        lock.lock();
        nowTimestamp = 0;
        try {
            nowTimestamp = Instant.now().toEpochMilli();
            if (lastTimestamp == nowTimestamp) {
                lastTimestamp = waitNextMilli();
            } else if (lastTimestamp > nowTimestamp) {
                throw new RuntimeException("time error when generated the id.");
            } else {
                lastTimestamp = nowTimestamp;
            }
        } finally {
            lock.unlock();
        }
        if (nowTimestamp == 0) {
            throw new RuntimeException("unknown error when generated the id.");
        }

        return nowTimestamp;
    }

    private long waitNextMilli() {
        //判斷是否進入下一毫秒
        //如果併發量特別高，會給cpu帶來額外負荷
        do {
            nowTimestamp = Instant.now().toEpochMilli();
        } while (nowTimestamp == lastTimestamp);
        return nowTimestamp;

        //直接睡一毫秒
//        try {
//            TimeUnit.MILLISECONDS.sleep(1);
//        } catch (InterruptedException e) {
//            e.printStackTrace();
//        }
//        nowTimestamp = Instant.now().toEpochMilli();
//        return nowTimestamp;
    }
}