手搓雪花ID算法-JAVA

最新推荐文章于 2025-12-28 16:49:38 发布

原创最新推荐文章于 2025-12-28 16:49:38 发布 · 812 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#java

本文介绍了一种基于SnowFlake算法的ID生成器实现，详细解释了其内部结构和工作原理，包括时间戳、工作机器ID及序列号的设计，并提供了具体的Java实现代码。

package com.licuncai.util;

/**
 * @author licuncai
 */
public class SnowFlake {

    // 起始时间 2020/1/1 00:00:00
    private final long startTime = 1577808000000L;

    // 序列段
    private long sequenceId = 0L;
    // 序列段位数
    private final long sequenceBits = 12L;
    // 序列段掩码
    private final long sequenceMask = ~(-1L << sequenceBits);
    // 序列段最大值
    private final long maxSequence = ~(-1L << sequenceBits);

    // 工作机器id
    private long workerId = 0L;
    // 工作机器位数
    private final long workerBits = 10L;
    // 工作机器掩码
    private final long workerMask = (~(-1L << (sequenceBits + workerBits)))^sequenceMask;
    // 工作机器最大值
    private final long maxWorker = ~(-1L << workerBits);

    // 时间戳
    private long timestamp = 0L;
    // 时间戳位数
    private final long timestampBits = 41L;
    // 时间戳掩码
    private final long timestampMask = ~((-1L << (sequenceBits + workerBits +timestampBits)) | sequenceMask | workerMask);

    public SnowFlake(Long workerId) throws IllegalArgumentException {
        if (workerId > maxWorker || workerId < 0)
            throw new IllegalArgumentException("workerId不能大于" + maxWorker + "，也不能小于0");
        this.workerId = workerId;
    }

    public SnowFlake() {}

    public synchronized long nextId() {
        long ts = System.currentTimeMillis();
        if (ts == timestamp) {
            if (++sequenceId > maxSequence) {
                while (ts == timestamp) {
                    timestamp = System.currentTimeMillis();
                }
                sequenceId = 0;
            }
        } else {
            timestamp = ts;
            sequenceId = 0;
        }
        return ((timestamp - startTime) << (sequenceBits + workerBits) & timestampMask) |
                ((workerId << sequenceBits) & workerMask) | (sequenceId & sequenceMask);
    }

}