雪花算法如何生成id-java教程

雪花算法生成id的方法：首先新建一个id生成的类；然后新建一个调用生成id的单例工具；最后使用函数【GuuidUtil.getUUID()】直接调用即可。

【相关学习推荐：java基础】

雪花算法生成id的方法：

1、新建一个id生成的类 SnowFlake

/** * @Auther: lyl * @Date: 2019/11/21 17:49 * @Description: */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     *     * @return     */    public synchronized long nextId() {        long currStmp = getNewstmp();        if (currStmp < lastStmp) {            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");        }        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;        }        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) {        SnowFlake snowFlake = new SnowFlake(2, 3);        for (int i = 0; i < (1 << 12); i++) {            System.out.println(snowFlake.nextId());        }    }}

2、为防止多线程生成重复的id，这边新建了一个调用生成id的单例工具

其中machineId和datacenterId可以放在配置文件中

import java.util.concurrent.CountDownLatch;/** * @Auther: lyl * @Date: 2019/11/21 18:15 * @Description: */public class GuuidUtil {    private static long machineId = 0;    private static long datacenterId = 0;    /**     * 单例模式创建学法算法对象     * */    private enum SnowFlakeSingleton{        Singleton;        private SnowFlake snowFlake;        SnowFlakeSingleton(){            snowFlake = new SnowFlake(datacenterId,machineId);        }        public SnowFlake getInstance(){            return snowFlake;        }    }    public static long getUUID(){        return SnowFlakeSingleton.Singleton.getInstance().nextId();    }    public static void main(String[] args) {         CountDownLatch latch = new CountDownLatch(10000);        long start = System.currentTimeMillis();        for (int i = 0; i < 10000; i++) {            new Runnable() {                @Override                public void run() {                    System.out.println(GuuidUtil.getUUID());                    latch.countDown();                }            }.run();        }        try {            System.out.println("主线程"+Thread.currentThread().getName()+"等待子线程执行完成...");            latch.await();//阻塞当前线程，直到计数器的值为0            System.out.println("主线程"+Thread.currentThread().getName()+"开始执行...");        } catch (InterruptedException e) {            e.printStackTrace();        }        System.out.print("雪花算法用时： ");        System.out.println(System.currentTimeMillis() - start);    }}

最后直接调用：GuuidUtil.getUUID()；就可以直接生成id

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