獲取各種隨機數的代碼工具類

2019-11-09 16:19:58

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package com.lyt.base.util;import java.text.DateFormat;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Date;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Random;public class RandomUtil {/*** 生成一個n位的隨機數字符串* * @param n* @return*/public static String getRandomNum(int length) {String str = "0123456789";Random random = new Random();StringBuffer sb = new StringBuffer();for (int i = 0; i < length; ++i) {int number = random.nextInt(9);// [1,9)sb.append(str.charAt(number+1));}return sb.toString();}/*** 生成一個n位的隨機字符串* * @param length* @return*/public static String getRandomString(int length) {String str = "abcdefghijklmnopqrstuvwxyz0123456789";Random random = new Random();StringBuffer sb = new StringBuffer();for (int i = 0; i < length; ++i) {int number = random.nextInt(36);// [0,36)sb.append(str.charAt(number));}return sb.toString();}/*** 獲取當前時間，年月日時* * @return*/public static String getDate() {String str = "";DateFormat df = new SimpleDateFormat("yyyyMMddHH");Date date = new Date();str = df.format(date);return str;}/*** 生成用戶id，10位,純數字* * @return*/public static String userId() {String userId = "";userId = getRandomNum(10);return userId;}/*** 生成訂單號，13位，純數字* * @return*/public static String orderId() {String orderId = "";String date = getDate();String rand = getRandomNum(13);orderId = date + rand;return orderId;}/*** 生成商品id，10位,純數字* * @return*/public static String PRoId() {String userId = "";userId = getRandomNum(10);return userId;}/*** 隨機取list數據 * @param list* @param n 取幾條* @return*/@SuppressWarnings({ "rawtypes", "unused", "unchecked" })public static List getRandomList(List list, int n) { Map map = new HashMap(); List listNew = new ArrayList(); if(list.size()<=n){ return list; }else{ while(map.size()<n){ int random = (int) (Math.random() * list.size()); if (!map.containsKey(random)) { map.put(random, ""); listNew.add(list.get(random)); } } return listNew; } }/*** 取數組隨機數* @param arr* @param n* @return*/@SuppressWarnings({ "unused", "unchecked" })public static Long[] createRandomArray(Long[] arr, int n) { // TODO Auto-generated method stub @SuppressWarnings("rawtypes")Map map = new HashMap(); Long[] arrNew = new Long[n]; if(arr.length<=n){ return arr; }else{ int count = 0;//新數組下標計數 while(map.size()<n){ int random = (int) (Math.random() * arr.length); if (!map.containsKey(random)) { map.put(random, ""); arrNew[count++] = arr[random]; } } return arrNew; } } }

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