[Java 11] System 类 与 Runtime 类

System

package com.qunar.basicJava.javase.p11CommonlyUsedClass;/** * Author: [e-mail]  Date: 14-5-21 10:54 */public class SystemDemo {    public static void main(String[] args) {        System.getProperties().list(System.out);        System.out.println("--------");        System.out.println("系统 ： " + System.getProperty("os.name"));        System.out.println("版本 ： " + System.getProperty("os.version") + System.getProperty("os.arch"));        System.out.println("当前用户 : " +  System.getProperty("user.name"));        System.out.println("当前用户工作目录 : " + System.getProperty("user.dir"));    }}

Runtime

package com.qunar.basicJava.javase.p11CommonlyUsedClass;/** * Author: [e-mail]  Date: 14-5-20 20:52 */public class RuntimeDemo01 {    public static void main(String[] args) {        Runtime run = Runtime.getRuntime(); // 静态方法，单例        System.out.println("JVM 最大内存量 : " + run.maxMemory());        System.out.println("JVM 最大内存量 : " + run.maxMemory() / 1024);        System.out.println("JVM 空闲内存量 : " + run.freeMemory() / 1024);        String str = "Hello" + "World!" + "hahaha" + "cost" + "iceTea";        System.out.println(str);        for (int i = 0; i < 10000; i++) {            str += i;        }        System.out.println("操作 String 之后，JVM 空闲内存量 : " + run.freeMemory() / 1024);        run.gc();        System.out.println("垃圾回收之后  ，  JVM 空闲内存量 : " + run.freeMemory() / 1024);//        run.exec("");    }}