Java 中网络相关 API 的应用

InetAddress的应用

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Arrays;

public class Test01 {

    public static void main(String[] args) throws UnknownHostException {
        //获取本机的InetAddress实例
        InetAddress address = InetAddress.getLocalHost();
        System.out.println("计算机名：" + address.getHostName());
        System.out.println("IP地址：" + address.getHostAddress());
        byte[] bytes = address.getAddress(); //获取字节数组形式的IP地址
        System.out.println("字节数组形式的IP地址：" + Arrays.toString(bytes));
        System.out.println(address); //直接输出InetAddress对象
        System.out.println();
        
        //根据机器名获取InetAddress实例
        //InetAddress address2 = InetAddress.getByName("DESKTOP-1GQCD7C");
        InetAddress address2 = InetAddress.getByName("10.4.44.26");
        System.out.println("计算机名：" + address2.getHostName());
        System.out.println("IP地址：" + address2.getHostAddress());
    }

}

以上来自慕课网

菜鸟教程：www.runoob.com/java/java-networking.html

 

URL的应用

URL常用方法

import java.net.MalformedURLException;
import java.net.URL;

/*
 * URL常用方法
 */

public class Test02 {
    public static void main(String[] args) {
        try {
            //创建一个URL实例
            URL imooc = new URL("http://www.imooc.com");
            //？后面表示参数，#后面表示锚点
            URL url = new URL(imooc,"/index.html?username:tom#test"); 
            System.out.println("协议：" + url.getProtocol());
            System.out.println("主机：" + url.getHost());
            //如果未指定端口号，则使用默认的端口号，此时getPort（）方法返回值为-1
            System.out.println("端口：" + url.getPort());
            System.out.println("文件路径：" + url.getPath());
            System.out.println("文件名：" + url.getFile());
            System.out.println("相对路径：" + url.getRef());
            System.out.println("查询字符串：" + url.getQuery());
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }
}

使用URL读取网页内容

1.通过URL对象的openStream()方法可以得到指定资源的输入流

2.通过输入流可以读取、访问网络上的数据

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;

/*
 * 使用URL读取网页内容
 */
public class Test03 {
    public static void main(String[] args) {
        try {
            //创建一个URL实例
            URL url = new URL("http://www.baidu.com");
            //通过URL的openStream方法获取URL对象所表示的资源的字节输入流
            InputStream is = url.openStream();
            //将字节输入流转换为字符输入流
            InputStreamReader isr = new InputStreamReader(is, "utf-8");
            //为字符输入流添加缓冲
            BufferedReader br = new BufferedReader(isr);
            String data = br.readLine();//读取数据
            while (data != null) {//循环读取数据
                System.out.println(data);//输出数据
                data = br.readLine();
            }
            br.close();
            isr.close();
            is.close();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}