Java基础--常用工具类

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网上一个链接

http://download.csdn.net/detail/xiyuan2016/9554252

Java 解析xml：dom4j、JDOMJava 解析Html：Jsoup

package com.test;import java.io.IOException;import java.util.Enumeration;import java.util.Map;import java.util.Properties;import java.util.Random;import java.util.concurrent.ThreadLocalRandom;public class SystemDemo {public static void main(String[] args) throws IOException {//获取操作系统环境变量Map<String, String> map = System.getenv();for (Map.Entry<String, String> entry : map.entrySet()) {System.out.println(entry.getKey()+"=====>"+entry.getValue());}System.out.println("--------------------------------------\n");//获取Java版本等信息Properties properties = System.getProperties();Enumeration<?> enumeration = properties.propertyNames();while (enumeration.hasMoreElements()) {System.out.println(enumeration.nextElement()+"=====>"+System.getProperty(String.valueOf(enumeration.nextElement())));}System.out.println("--------------------------------------\n");//RunningRuntime runtime = Runtime.getRuntime();System.out.println("总内存="+runtime.totalMemory());System.out.println("可用内存="+runtime.freeMemory());System.out.println("处理器数量="+runtime.availableProcessors());//打开QQ//runtime.exec("C:\\Program Files (x86)\\Tencent\\QQ\\Bin\\QQScLauncher.exe");//范围随机数Random random = new Random();System.out.println(random.nextInt(50));//0-49ThreadLocalRandom random2 = ThreadLocalRandom.current();int value = random2.nextInt(2, 5);//2-4System.out.println(value);}}

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