java===System

package 常用类.System;
/**
 * Properties 集合中都是String类型的建和值*/
import java.util.Properties;
import java.util.Set;

public class SystemDemo {
    private static final String LINE_SEPARATOR =System.getProperty("line.separator"); 
    //获取当前操作系统换行命令代码
    public static void main(String[] args) {
        System.out.println("Hello"+LINE_SEPARATOR+"World");
        //得到系统属性,这个方法返回的是一个Properties集合，是map子类；
        Properties prop = System.getProperties();
        //设置系统属性
        System.setProperty("webdriver.chrome.driver", "C:\chrome.driver");
        Set<String> nameSet = prop.stringPropertyNames();//获取键的set集合
        for(String key:nameSet){
            String value=prop.getProperty(key);
            System.out.println(key+"::"+value);
        }

    }

}

package 常用类.System;

import java.util.Properties;
import java.util.Set;

public class SystemTest {

    public static void main(String[] args) {
        demo_1();
        demo_2();
        demo_3();

    }
    public static void demo_3() {
        final String LINE_SEPARATOR=System.getProperty("line.separator");
        System.out.println("Hello"+LINE_SEPARATOR+"World");
        System.setProperty("webdriver.ie.driver", "C:\IE");
    }
    public static void demo_2() {
        Properties prop1=System.getProperties();
        Set<String> keySet=prop1.stringPropertyNames();
        for(String s1:keySet){
            String value = prop1.getProperty(s1);
            System.out.println(s1+":"+value);
        }
        
    }
    public static void demo_1(){
        //获取当前时间的毫秒值
        Long l1=System.currentTimeMillis();
        System.out.println(l1);
    } 

}