java 生成15位分布式数字ID

可以使用Snowflake算法来生成分布式数字ID。Snowflake算法可以生成一个64位的ID，其中包含了时间戳、机器ID和序列号。下面是一个Java实现的示例代码，可以生成15位的分布式数字ID：

public class SnowflakeIdWorker {
    // 开始时间戳（2022-01-01 00:00:00）
    private final long twepoch = 1640995200000L;
    // 机器ID所占的位数
    private final long workerIdBits = 5L;
    // 数据标识ID所占的位数
    private final long datacenterIdBits = 5L;
    // 支持的最大机器ID，结果是31
    private final long maxWorkerId = ~(-1L << workerIdBits);
    // 支持的最大数据标识ID，结果是31
    private final long maxDatacenterId = ~(-1L << datacenterIdBits);
    // 序列号所占的位数
    private final long sequenceBits = 12L;
    // 机器ID向左移12位
    private final long workerIdShift = sequenceBits;
    // 数据标识ID向左移17位（12+5）
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    // 时间戳向左移22位（5+5+12）
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    // 生成序列的掩码，这里为4095
    private final long sequenceMask = ~(-1L << sequenceBits);

    private long workerId;
    private long datacenterId;
    private long sequence = 0L;
    private long lastTimestamp = -1L;

    public SnowflakeIdWorker(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;
    }

    /**
     * 产生下一个ID
     *
     * @return SnowflakeId
     */
    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) {
            // 相同毫秒内，序列号自增
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                // 同一毫秒的序列号已经用完，等待下一毫秒
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 不同毫秒内，序列号重置
            sequence = 0L;
        }

        lastTimestamp = timestamp;

        // 时间戳部分
        long id = (timestamp - twepoch) << timestampLeftShift;
        // 数据标识ID部分
        id |= datacenterId << datacenterIdShift;
        // 机器ID部分
        id |= workerId << workerIdShift;
        // 序列号部分
        id |= sequence;

        return id;
    }

    /**
     * 等待下一个毫秒的到来
     *
     * @param lastTimestamp 上次生成ID的时间戳
     * @return 当前时间戳
     */
    private long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    /**
     * 获取当前的时间戳
     *
     * @return 当前时间戳
     */
    private long timeGen() {
        return System.currentTimeMillis();
    }
}

使用示例：

SnowflakeIdWorker idWorker = new SnowflakeIdWorker(1, 1);
long id = idWorker.nextId();
System.out.println(id);

输出结果为一个15位的数字ID，例如：

246168155236608