获取下载文件的文件名和分段下载

Question

Here is my code for downloading a file from a specified URL using a thread. I want to make it to a multi-threading download, but i cant work it out. And i want to get the downloaded filename is the same as name of the file on URL + part.1,2,3.. etc. Can u guys help me out ? and sorry for my bad english grammar ! My favorite link for test this is : https://docs.oracle.com/javaee/7/JEETT.pdf Thannks all in advance !

public class Threadtest extends Thread {
    String s ;

    public void InputUrl(){

        Scanner sc = new Scanner(System.in);
        System.out.println("Input URL :");
        s = sc.nextLine();


    }   
    public void run(){

        BufferedInputStream bis = null ;
        RandomAccessFile raf = null ; 
        HttpURLConnection conn = null;
        URL mUrl = null ;
        String a = new File(mUrl.getPath().toString()).getName();           
         try{

             mUrl = new URL(s);
              conn = (HttpURLConnection)mUrl.openConnection();
              String byteRange = 0+ "-" + 1024;
                conn.setRequestProperty("Range", "bytes=" + byteRange);

             conn.connect();    
             bis = new BufferedInputStream(conn.getInputStream());
                raf = new RandomAccessFile(a, "rw");
                raf.seek(0);

             byte[] buffer = new byte[4092];
             int count = 0 ;
             while ((count = bis.read(buffer,0,4092))!= -1)
             {

                raf.write(buffer, 0 ,count);
             }
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

} 

Answer 1

Extending Thread is not so good idea. Better, by philosophical reason, is to implements Runnable interface.

class DownloadTask implements Runnable {

    private final URL url;

    DownloadTask(URL url) {
        this.url = url;
    }

    @Override
    public void run() {
        // download code
    }
}

now we have code to download only. Next step is to use Executor Framework to execute our download tasks.

class Downloader{

    private static boolean exitFlag;

    public static void main(String[] args) {
        ExecutorService pool = Executors.newCachedThreadPool();
        while(exitFlag) {
            URL fileUrl = readUrlFromUserOrSetExit();
            pool.execute(new DownloadTask(fileUrl));
        }
        pool.shutdown();
    }

    private static URL readUrlFromUserOrSetExit() {
        // read from user of set exit flag
    }
}

How does it works?

• You create executor named pool that is responsible for all "thread magic".
• while user not put exit command you read file URL
• create DownloadTask instance
• send it to pool to execute .
• if user put exit command then you shutdown executor.

It is probably the easiest way if you don't want to use external libs.