URL

统一资源定位符：定位资源的，定位互联网上的某一个资源

DNS域名解析   www.baidu.com--->ip

协议://ip地址:端口/项目名/资源

URL类：

package com.wzz.A04网络编程;

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

public class B07URL {
    public static void main(String[] args) throws MalformedURLException {
        URL url = new URL("https://www.py.cn/code/31340.html");
        System.out.println(url.getProtocol());//协议
        System.out.println(url.getHost());//主机ip
        System.out.println(url.getPort());//端口
        System.out.println(url.getPath());//全路径
        System.out.println(url.getFile());//文件
        System.out.println(url.getQuery());//参数
    }
}

资源下载：

package com.wzz.A04网络编程;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;

public class B08UrlDown {
    public static void main(String[] args) throws Exception {
        //1.下载地址
        URL url = new URL("https://m701.music.126.net/20211020174755/6f13a2547ae41b05a80fb9bba778cc2e/jdyyaac/565b/065f/0358/a1cd0e25a815dffcc0c1422398efde9e.m4a");
        //2.连接到这个资源 HTTP
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("起风了.mv4");

        byte[] buffer = new byte[1024];
        int len;
        while ((len=inputStream.read(buffer))!=-1){
            fos.write(buffer,0,len);//写出这个数据
        }

        fos.close();
        inputStream.close();
        urlConnection.disconnect();//断开连接
    }
}