生成唯一id写法，雪花算法

这个工具直接调用就可以了，用法和写法如下：

代码：

这个是雪花算法的写法：

 1 public class SnowFlakeUtil {
 2
 3     /**
 4      * 起始的时间戳
 5      */
 6     private final static long START_STMP = 1480166465631L;
 7
 8     /**
 9      * 每一部分占用的位数
10      */
11     private final static long SEQUENCE_BIT = 12; //序列号占用的位数
12     private final static long MACHINE_BIT = 5;  //机器标识占用的位数
13     private final static long DATACENTER_BIT = 5;//数据中心占用的位数
14
15     /**
16      * 每一部分的最大值
17      */
18     private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
19     private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
20     private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
21
22     /**
23      * 每一部分向左的位移
24      */
25     private final static long MACHINE_LEFT = SEQUENCE_BIT;
26     private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
27     private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
28
29     private long datacenterId;  //数据中心
30     private long machineId;    //机器标识
31     private long sequence = 0L; //序列号
32     private long lastStmp = -1L;//上一次时间戳
33
34     public SnowFlakeUtil(long datacenterId, long machineId) {
35         if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
36             throw new IllegalArgumentException("datacenterId can‘t be greater than MAX_DATACENTER_NUM or less than 0");
37         }
38         if (machineId > MAX_MACHINE_NUM || machineId < 0) {
39             throw new IllegalArgumentException("machineId can‘t be greater than MAX_MACHINE_NUM or less than 0");
40         }
41         this.datacenterId = datacenterId;
42         this.machineId = machineId;
43     }
44
45     /**
46      * 产生下一个ID
47      *
48      * @return
49      */
50     public synchronized long nextId() {
51         long currStmp = getNewstmp();
52         if (currStmp < lastStmp) {
53             throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
54         }
55
56         if (currStmp == lastStmp) {
57             //相同毫秒内，序列号自增
58             sequence = (sequence + 1) & MAX_SEQUENCE;
59             //同一毫秒的序列数已经达到最大
60             if (sequence == 0L) {
61                 currStmp = getNextMill();
62             }
63         } else {
64             //不同毫秒内，序列号置为0
65             sequence = 0L;
66         }
67
68         lastStmp = currStmp;
69
70         return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
71                 | datacenterId << DATACENTER_LEFT      //数据中心部分
72                 | machineId << MACHINE_LEFT            //机器标识部分
73                 | sequence;                            //序列号部分
74     }
75
76     private long getNextMill() {
77         long mill = getNewstmp();
78         while (mill <= lastStmp) {
79             mill = getNewstmp();
80         }
81         return mill;
82     }
83
84     private long getNewstmp() {
85         return System.currentTimeMillis();
86     }
87 //小测试代码:
88
89 //    public static void main(String[] args) {
90 //        SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);
91 //
92 //            System.out.println(snowFlake.nextId());
93 //
94 //    }
95 }

具体的调用：

 1 import java.text.SimpleDateFormat;
 2 import java.util.Date;
 3 import java.util.Random;
 4
 5 public class CreateAUniqueIDUtil {
 6     public String ImageID(String subtype) {
 7         SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);//调用雪花算法生成18位唯一id
 8         long randomNumber18 = snowFlake.nextId();//18位唯一id
 9         Random rand = new Random();//生成随机数
10         String cardNnumer = "";
11         for (int a = 0; a < 2; a++) {
12             cardNnumer += rand.nextInt(10);//生成2位随机数
13         }
14 //        String subtype = "01";//01代表的是对应应用中解析时的参数，当前01代表 人员
15         String randomNumberString = "";
16         for (int a = 0; a < 5; a++) {
17             randomNumberString += rand.nextInt(10);//生成5位数字
18         }
19         Date date = new Date();
20         SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
21         String format = df.format(date);
22         String ImageID = randomNumber18 + cardNnumer + subtype + format + randomNumberString;
23         return ImageID;
24     }
25
26     public String PersonID(String subtype) {
27         SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);//调用雪花算法生成18位唯一id
28         long randomNumber18 = snowFlake.nextId();//18位唯一id
29         Random rand = new Random();//生成随机数
30         String cardNnumer = "";
31         for (int i = 0; i < 23; i++) {
32             cardNnumer += rand.nextInt(10);//生成23位随机数
33         }
34 //        String subtype = "01";//01-人员
35         String randomNumberString = "";
36         for (int a = 0; a < 5; a++) {
37             randomNumberString += rand.nextInt(10);//生成5位数字
38         }
39         String PersonID = randomNumber18 + cardNnumer + subtype + randomNumberString;
40         return PersonID;
41     }
42
43     public String SourceID(String subtype) {
44         SnowFlakeUtil snowFlake = new SnowFlakeUtil(2, 3);//调用雪花算法生成18位唯一id
45         long randomNumber18 = snowFlake.nextId();//18位唯一id
46         Random rand = new Random();//生成随机数
47         String cardNnumer = "";
48         for (int i = 0; i < 2; i++) {
49             cardNnumer += rand.nextInt(10);//生成2位随机数
50         }
51 //        String subtype = "02";//01-人员02-机动车03-非机动车04-物品05-场景06-人脸等
52         Date date = new Date();
53         SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
54         String format = df.format(date);
55         String randomNumberString = "";
56         for (int a = 0; a < 5; a++) {
57             randomNumberString += rand.nextInt(10);//生成5位数字
58         }
59         String SourceID = randomNumber18 + cardNnumer + subtype + format + randomNumberString;
60         return SourceID;
61     }
62 }

原文地址：https://www.cnblogs.com/wangquanyi/p/11328943.html