雪花算法代码java

雪花算法是一种分布式系统中生成唯一ID的算法，它可以保证在不同的机器上生成的ID是唯一的。以下是雪花算法的Java代码实现：

public class SnowflakeDistributeId {
    // 起始的时间戳
    private final static long START_STMP = 1480166465631L;    // 每一部分占用的位数，就三个，分别代表时间戳、机器标识符和序列号
    private final static long SEQUENCE_BIT = 12; // 序列号占用的位数
    private final static long MACHINE_BIT = 5; // 机器标识符占用的位数
    private final static long DATACENTER_BIT = 5; // 数据中心占用的位数
    // 每一部分的最大值
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
    // 每一部分向左的位移
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
    private long datacenterId; // 数据中心
    private long machineId; // 机器标识符
    private long sequence = 0L; // 序列号
    private long lastStmp = -1L; // 上一次时间戳
    public SnowflakeDistributeId(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }
    public synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }
        if (currStmp == lastStmp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            sequence = 0L;
        }
        lastStmp = currStmp;
        return (currStmp - START_STMP) << TIMESTMP_LEFT // 时间戳部分
                | datacenterId << DATACENTER_LEFT // 数据中心部分
                | machineId << MACHINE_LEFT // 机器标识符部分
                | sequence; // 序列号部分
    }
    private long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }
    private long getNewstmp() {
        return System.currentTimeMillis();
    }
}

这段代码实现了一个SnowflakeDistributeId类，它包含了数据中心ID和机器ID两个参数，通过调用nextId()方法可以生成一个唯一的ID。