雪花算法生成id的方法

小編給大家分享一下雪花算法生成id的方法，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！

雪花算法生成id的方法：首先新建一個id生成的類；然后新建一個調用生成id的單例工具；最后使用函數【GuuidUtil.getUUID()】直接調用即可。

雪花算法生成id的方法：

1、新建一個id生成的類 SnowFlake

/**
 * @Auther: lyl
 * @Date: 2019/11/21 17:49
 * @Description:
 */
public class SnowFlake {
    /**
     * 起始的時間戳
     */
    private final static long START_STMP = 1480166465631L;
    /**
     * 每一部分占用的位數
     */
    private final static long SEQUENCE_BIT = 12; //序列號占用的位數
    private final static long MACHINE_BIT = 5;  //機器標識占用的位數
    private final static long DATACENTER_BIT = 5;//數據中心占用的位數
    /**
     * 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;  //數據中心
    private long machineId;    //機器標識
    private long sequence = 0L; //序列號
    private long lastStmp = -1L;//上一次時間戳
    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;
    }
    /**
     * 產生下一個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) {
            //相同毫秒內，序列號自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            //同一毫秒的序列數已經達到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            //不同毫秒內，序列號置為0
            sequence = 0L;
        }
        lastStmp = currStmp;
        return (currStmp - START_STMP) << TIMESTMP_LEFT //時間戳部分
                | datacenterId << DATACENTER_LEFT      //數據中心部分
                | machineId << MACHINE_LEFT            //機器標識部分
                | sequence;                            //序列號部分
    }
    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、為防止多線程生成重復的id，這邊新建了一個調用生成id的單例工具

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;
    /**
     * 單例模式創建學法算法對象
     * */
    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("主線程"+Thread.currentThread().getName()+"等待子線程執行完成...");
            latch.await();//阻塞當前線程，直到計數器的值為0
            System.out.println("主線程"+Thread.currentThread().getName()+"開始執行...");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.print("雪花算法用時： ");
        System.out.println(System.currentTimeMillis() - start);
    }
}

最后直接調用：GuuidUtil.getUUID()；就可以直接生成id

以上是雪花算法生成id的方法的所有內容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內容對大家有所幫助，如果還想學習更多知識，歡迎關注億速云行業資訊頻道！