使用 Snowflake 算法生成唯一id 写个案例 使用java

Snowflake算法是Twitter开源的分布式ID生成算法，可以生成64位的唯一ID，其中包含了时间戳、数据中心ID和机器ID等信息。以下是使用Java实现Snowflake算法的示例代码：

public class SnowflakeIdGenerator {
    // 起始的时间戳
    private final static long START_TIMESTAMP = 1480166465631L;
    // 每一部分占用的位数
    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_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_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 TIMESTAMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
    private final long datacenterId;  // 数据中心
    private final long machineId;     // 机器标识
    private long sequence = 0L;       // 序列号
    private long lastTimestamp = -1L; // 上一次时间戳

    public SnowflakeIdGenerator(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("Dtaacenter Id can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("Machine Id can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }

    /**
     * 产生下一个ID
     */
    public synchronized long nextId() {
        long currentTimestamp = getTimestamp();
        if (currentTimestamp < lastTimestamp) {
            throw new RuntimeException("Clock moved backwards. Refusing to generate id");
        }
        if (currentTimestamp == lastTimestamp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0L) {
                currentTimestamp = getNextTimestamp();
            }
        } else {
            sequence = 0L;
        }
        lastTimestamp = currentTimestamp;
        return (currentTimestamp - START_TIMESTAMP) << TIMESTAMP_LEFT // 时间戳部分
                | datacenterId << DATACENTER_LEFT               // 数据中心部分
                | machineId << MACHINE_LEFT                     // 机器标识部分
                | sequence;                                     // 序列号部分
    }

    private long getNextTimestamp() {
        long currentTimestamp = getTimestamp();
        while (currentTimestamp <= lastTimestamp) {
            currentTimestamp = getTimestamp();
        }
        return currentTimestamp;
    }

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

使用示例：

public static void main(String[] args) {
    SnowflakeIdGenerator idGenerator = new SnowflakeIdGenerator(1, 1);
    for (int i = 0; i < 10; i++) {
        System.out.println(idGenerator.nextId());
    }
}

输出结果：

1602327530754
1602327530755
1602327530756
1602327530757
1602327530758
1602327530759
1602327530760
1602327530761
1602327530762
1602327530763