Java中SnowFlake 雪花算法生成全局唯一id中的问题,时间不连续全为偶数解决

package com.example.springbootshardingjdbc.util;

import java.io.FileOutputStream;

/**
 * 描述: Twitter的分布式自增ID雪花算法snowflake (Java版)
 *
 * @author
 * @create 2018-03-13 12:37
 **/
public class SnowFlake {

    /**
     * 起始的时间戳
     */
    private final static long START_STMP = 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_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
    private long sequence = 0L; //序列号
    private long lastStmp = -1L;//上一次时间戳

    public SnowFlake(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;
    }

    /**
     * 产生下一个ID
     *
     * @param ifEvenNum 是否偶数 true 时间不连续全是偶数  时间连续 奇数偶数 false 时间不连续 奇偶都有  所以一般建议用false
*
@return */ public synchronized long nextId(boolean ifEvenNum) { long currStmp = getNewstmp(); if (currStmp < lastStmp) { throw new RuntimeException("Clock moved backwards. Refusing to generate id"); } /** * 时间不连续出来全是偶数 */ if(ifEvenNum){ if (currStmp == lastStmp) { //相同毫秒内,序列号自增 sequence = (sequence + 1) & MAX_SEQUENCE; //同一毫秒的序列数已经达到最大 if (sequence == 0L) { currStmp = getNextMill(); } } else { //不同毫秒内,序列号置为0 sequence = 0L; } }else { //相同毫秒内,序列号自增 sequence = (sequence + 1) & MAX_SEQUENCE; } 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(); } public static void main(String[] args) throws Exception{ /** * 分布式数据中心id * 机器id */ SnowFlake snowFlake = new SnowFlake(5, 6); for (int i = 0; i < 10; i++) { /** * 时间连续 奇数偶数都有 */ //System.out.println(snowFlake.nextId(true)); /** * 429407369643581440 * 429407369643581441 * 429407369643581442 * 429407369643581443 * 429407369643581444 * 429407369643581445 * 429407369643581446 * 429407369643581447 * 429407369643581448 * 429407369643581449 */ //System.out.println(snowFlake.nextId(true)); /** * 时间不连续 原版 获取的id全是偶数 */ //Thread.sleep(1); /** * 429407954194935808 * 429407954199130112 * 429407954207518720 * 429407954211713024 * 429407954215907328 * 429407954224295936 * 429407954249461760 * 429407954253656064 * 429407954257850368 * 429407954262044672 */ long snowFlakeId = snowFlake.nextId(false); System.out.println(snowFlakeId); /** * 时间不连续 改版 获取的id为奇偶数 */ Thread.sleep(1); /** * 429408617683496961 * 429408617691885570 * 429408617696079875 * 429408617700274180 * 429408617704468485 * 429408617708662790 * 429408617712857095 * 429408617717051400 * 429408617725440009 * 429408617729634314 */ } } }

 

文章来自:https://www.cnblogs.com/coderdxj/p/12358500.html
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