Question

I am trying to interrupt a thread that is running AES encryption on a file. That can take a while, so far I have come up with this.

This body is inside button activate event. When the user clicks the button again (else clause). The thread should be interrupted, but I would be happier if I could stop the thread completely. But that is deprecated.

Anyway, the thread ignores the .interrupt() and continues to execute the aes256File. It does raise the fileEncryptThread.isInterrupted() flag, but from cpu usage I can see it still continues to crunch the file.

I have read the guide on safe stopping of threads, but I have no desire to completely redesign my already slow AES implementation to be checking for out of class interrupts flags…

    fileEncryptThread = new FileThread() // new thread please
    {
        @Override
        public void run()
        {
            String result = "";
            result = MyCrypto.aes256File(enInPath,
                                         enOutPath, 
                                         charsToString(passT.getPassword()),
                                         sec);
            if (!"".equals(result)) // error handling
            {
                JOptionPane.showMessageDialog(null,result);
            }
        }
    };
    fileEncryptThread.start();
  }
  else // if stop clicked
  {
      fileEncryptThread.interrupt();

Answer 1

AFAIK, the only safe way for a thread to terminate is to return from the “main”-method of the thread (usually run() in Runnable or Thread). You could for example use a while(<some class member boolean>) -loop inside your MyCrypto.aes256File -method and set the boolean to false so the thread will fall out of the loop and exit returning a value indicating that the process was not completed.