雪花算法如何生成id

互联网 20-8-31

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