生成唯一id寫法，雪花算法

這個工具直接調用就可以了，用法和寫法如下：

代碼：

這個是雪花算法的寫法：

public class SnowFlakeUtil {

    /**
     * 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 SnowFlakeUtil(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();
    }
//小測試代碼:

//    public static void main(String[] args) {
//        SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);
//
//            System.out.println(snowFlake.nextId());
//
//    }
}

具體的調用：

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;

public class CreateAUniqueIDUtil {
    public String ImageID(String subtype) {
        SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);//調用雪花算法生成18位唯一id
        long randomNumber18 = snowFlake.nextId();//18位唯一id
        Random rand = new Random();//生成隨機數
        String cardNnumer = "";
        for (int a = 0; a < 2; a++) {
            cardNnumer += rand.nextInt(10);//生成2位隨機數
        }
//        String subtype = "01";//01代表的是對應應用中解析時的參數，當前01代表 人員
        String randomNumberString = "";
        for (int a = 0; a < 5; a++) {
            randomNumberString += rand.nextInt(10);//生成5位數字
        }
        Date date = new Date();
        SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
        String format = df.format(date);
        String ImageID = randomNumber18 + cardNnumer + subtype + format + randomNumberString;
        return ImageID;
    }

    public String PersonID(String subtype) {
        SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);//調用雪花算法生成18位唯一id
        long randomNumber18 = snowFlake.nextId();//18位唯一id
        Random rand = new Random();//生成隨機數
        String cardNnumer = "";
        for (int i = 0; i < 23; i++) {
            cardNnumer += rand.nextInt(10);//生成23位隨機數
        }
//        String subtype = "01";//01-人員
        String randomNumberString = "";
        for (int a = 0; a < 5; a++) {
            randomNumberString += rand.nextInt(10);//生成5位數字
        }
        String PersonID = randomNumber18 + cardNnumer + subtype + randomNumberString;
        return PersonID;
    }

    public String SourceID(String subtype) {
        SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);//調用雪花算法生成18位唯一id
        long randomNumber18 = snowFlake.nextId();//18位唯一id
        Random rand = new Random();//生成隨機數
        String cardNnumer = "";
        for (int i = 0; i < 2; i++) {
            cardNnumer += rand.nextInt(10);//生成2位隨機數
        }
//        String subtype = "02";//01-人員02-機動車03-非機動車04-物品05-場景06-人臉等
        Date date = new Date();
        SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
        String format = df.format(date);
        String randomNumberString = "";
        for (int a = 0; a < 5; a++) {
            randomNumberString += rand.nextInt(10);//生成5位數字
        }
        String SourceID = randomNumber18 + cardNnumer + subtype + format + randomNumberString;
        return SourceID;
    }
}