例如：https://www.baidu.com

URL【統一資源定位符】：定位資源的，定位網際網路上的某一個資源。

DNS 域名解析：www.baidu.com【某一域名】指向 39.156.69.79【某一網站空間IP】

URL 組成：協議://ip地址:埠/專案名/資源

URL：統一資源定位符

package lesson04;

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

/**
 * URL：統一資源定位符
 */
public class URLDemo1 {

    public static void main(String[] args) throws
 
 MalformedURLException {
        URL url = new URL("http://localhost:8080/helloworld/index.jsp?username=kuangshen&password=123");
        //協議名
        System.out.println(url.getProtocol());
        //主機名-主機ip
        System.out.println(url.getHost());
        //埠
        System.out.println(url.getPort());
        
 
//地址-檔案路徑
        System.out.println(url.getPath());
        //檔案-全路徑
        System.out.println(url.getFile());
        //查詢部分-引數
        System.out.println(url.getQuery());
    }

}

URL下載資源

package lesson04;

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

/**
 * URL下載資源
 */
public class URLDown {

    public static void main(String[] args) throws Exception {
        //1、下載地址
        URL url = new URL("https://m10.music.126.net/20201121104035/2c5eb73ce4421a090b62647f6c486e2c/yyaac/obj/wonDkMOGw6XDiTHCmMOi/3625445007/7d37/4109/d0ef/d56e8176f5789a4e6f8b2173ce500bf6.m4a");

        //2、連線到這個資源 HTTP
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("f6.m4a");

        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer)) != -1){
            fos.write(buffer, 0, len); //寫出這個資料
        }

        //關閉
        fos.close();
        inputStream.close();

        //斷開連線
        urlConnection.disconnect();
    }

}

效果一覽