package com.ruoyi.common.utils;
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import java.util.Random;
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/**
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* Created by zhuweiping
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* 随机数工具类
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* on 2021/4/8.
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*/
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public class RandomUtils {
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/**
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* 生成指定位数数字随机数字
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* @param n
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* @return
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*/
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public static String random(int n) {
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if (n < 1 || n > 10) {
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throw new IllegalArgumentException("cannot random " + n + " bit number");
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}
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Random ran = new Random();
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if (n == 1) {
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return String.valueOf(ran.nextInt(10));
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}
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int bitField = 0;
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char[] chs = new char[n];
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for (int i = 0; i < n; i++) {
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while(true) {
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int k = ran.nextInt(10);
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if( (bitField & (1 << k)) == 0) {
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bitField |= 1 << k;
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chs[i] = (char)(k + '0');
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break;
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}
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}
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}
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return new String(chs);
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}
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/**
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* 生成带时间+随机数 字符串
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* @param prefix 前缀
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* @param randomNum 随机数位置
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* @return
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*/
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public static String getDateTimeNowRandom(String prefix,int randomNum){
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try{
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return prefix+DateUtils.dateTimeNow()+ random(randomNum);
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}catch (Exception e){
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return "";
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}
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}
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/**
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* 生成带时间+随机数 字符串
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* @param prefix 前缀
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* @param randomNum 随机数位置
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* @return
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*/
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public static String getDateTimeNowRandom(String prefix,String suffix,int randomNum){
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try{
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return prefix+DateUtils.dateTimeNow()+ random(randomNum)+suffix;
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}catch (Exception e){
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return "";
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}
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}
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public static void main(String[] args)
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{
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String A = "2";
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Long b = Long.valueOf(A);
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System.out.println(random(4));
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}
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}
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