[Java 11] System 类 与 Runtime 类

System

package com.qunar.basicJava.javase.p11CommonlyUsedClass;

/**
 * Author: libin.chen@qunar.com  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: libin.chen@qunar.com  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("");

    }
}