multithreading - Java: Force stopping of ExecutorService threads

Question

My code:

String[] torrentFiles = new File("/root/torrents/").list();

        if(torrentFiles.length == 0 || torrentFiles == null)
        {
            System.exit(0);
        }

        ex = Executors.newFixedThreadPool(3);

        for(String torrentFile : torrentFiles)
        {
            ex.submit(new DownloadTorrent("/root/torrents/" + torrentFile));
        }

        ex.shutdown();

        try
        {
            ex.awaitTermination(30, TimeUnit.MINUTES);
        }
        catch(InterruptedException ex1)
        {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex1);
        }

But sometimes torrent downloading takes unknown time value and ?awaitTermination? not works as I want. I need to stop all executed threads instantly after half an hour but as I know ?awaitTermination? just only use interrupt() method which works only in loops or waiting. So timeout not works if this moment happens. So, how to?

Answer 1

Instant thread termination is never guaranteed, unless the thread checks periodically for isInterrupted() flag (or is waiting in interruptable method, i.e. which throws InterruptedException).

Consider implementing your worker threads in manner, when they check periodically for isInterrupted(). This may be something like that:

public void run() { 
  byte[] data;
  do {
     data = receiveDataChunk(timeout);
     processData(data);
  } while(!isInterrupted() && data != null);
}