生成唯一不重复的随机数

  1. 在日常开发中需要通过程序生成一系列不重复的随机数,通过Java自带的类库也可以实现，但是在高并发情况下会出现重复的情况，为了尽可能解决不重复的问题，我们通过根据ip地址，MAC地址，访问时间以及哈希算法生成唯一不重复的唯一编号以及访问IP地址获取
  2. 根据UUID全球唯一标识符也可以实现不重复的编号，具体代码如下
  3.   1 package com.sun.generat;
  2 
  3 import java.net.InetAddress;
  4 import java.util.Random;
  5 import java.util.UUID;
  6 
  7 /**
  8 * @ClassName: UUIDHexGenerator
  9 * @Description:生成不重复的随机数
 10 * @author sunt
 11 * @date 2017年8月17日 上午11:09:27
 12 */ 
 13 public class UUIDHexGenerator {
 14 
 15      private String sep = "";
 16         private static final int IP;
 17         static {
 18             int ipadd;
 19             try {
 20                 ipadd = toInt(InetAddress.getLocalHost().getAddress());
 21             } catch (Exception e) {
 22                 ipadd = 0;
 23             }
 24             IP = ipadd;
 25         }
 26         private static short counter = (short) 0;
 27         private static final int JVM = (int) (System.currentTimeMillis() >>> 8);
 28 
 29         public static int toInt(byte[] bytes) {
 30             int result = 0;
 31             for (int i = 0; i < 4; i++) {
 32                 result = (result << 8) - Byte.MIN_VALUE + (int) bytes[i];
 33             }
 34             return result;
 35         }
 36 
 37         /**
 38          * Unique in a local network
 39          */
 40         protected int getIP() {
 41             return IP;
 42         }
 43 
 44         /**
 45          * Unique down to millisecond
 46          */
 47         protected short getHiTime() {
 48             return (short) (System.currentTimeMillis() >>> 32);
 49         }
 50 
 51         protected int getLoTime() {
 52             return (int) System.currentTimeMillis();
 53         }
 54 
 55         /**
 56          * Unique across JVMs on this machine (unless they load this class in the
 57          * same quater second - very unlikely)
 58          */
 59         protected int getJVM() {
 60             return JVM;
 61         }
 62 
 63         protected String format(int intval) {
 64             String formatted = Integer.toHexString(intval);
 65             StringBuffer buf = new StringBuffer("00000000");
 66             buf.replace(8 - formatted.length(), 8, formatted);
 67             return buf.toString();
 68         }
 69 
 70         protected String format(short shortval) {
 71             String formatted = Integer.toHexString(shortval);
 72             StringBuffer buf = new StringBuffer("0000");
 73             buf.replace(4 - formatted.length(), 4, formatted);
 74             return buf.toString();
 75         }
 76 
 77         public String generate() {
 78             return new StringBuilder(36).append(format(getIP())).append(sep)
 79                     .append(format(getJVM())).append(sep)
 80                     .append(format(getHiTime())).append(sep)
 81                     .append(format(getLoTime())).append(sep)
 82                     .append(format(getCount())).toString();
 83         }
 84 
 85         /**
 86          * Unique in a millisecond for this JVM instance (unless there are >
 87          * Short.MAX_VALUE instances created in a millisecond)
 88          */
 89         protected short getCount() {
 90             synchronized (UUIDHexGenerator.class) {
 91                 if (counter < 0)
 92                     counter = 0;
 93                 return counter++;
 94             }
 95         }
 96 
 97         public static void main(String[] args) {
 98             UUIDHexGenerator uuidHexGenerator = new UUIDHexGenerator();
 99             String generate = uuidHexGenerator.generate();
100             System.out.println("---------generate:" + generate);
101             int num = uuidHexGenerator.getIP();
102             System.out.println("生成的随机数:" + num);
103             System.out.println(UUID.randomUUID().toString());
104             System.out.println(UUID.randomUUID().toString().replaceAll("\\-", ""));
105             
106         }
107 }

     

posted @ 2017-08-17 11:22  sunny1009  阅读(751)  评论(0)  编辑  收藏  举报