思路：1.下载的地址

           2.连接到这个资源

           3.创建输入流，创建输出流

           4.缓冲区

           5.写出数据

           6.断开连接

====================================

public class UrlDown {
    public static void main(String[] args) throws IOException {
        //下载地址
        String s=new String();
        s="https://webfs.ali.kugou.com/202112141346/700a7e20667d5f9fa312d84b29c000df/part/0/960125/KGTX/CLTX001/6e5709f6ba796690b68c66e4bde4fbb5.mp3";
        URL url=new URL(s);
        //连接到这个资源
        HttpURLConnection urlConnection=(HttpURLConnection) url.openConnection();
        InputStream inputStream=urlConnection.getInputStream();
        FileOutputStream fos=new FileOutputStream("2.mp3");//输出文件地址
        //缓冲区
        byte[] buffer=new byte[1024];
        int len;
        while ((len=inputStream.read(buffer))!=-1){
            fos.write(buffer,0,len);//写出数据
        }
        fos.close();。//先建后关
        inputStream.close();
        urlConnection.disconnect();//断开连接
    }
}