如何在Java中停止正在运行的Thread

Question

I am using a Java based file conversion tool which converts PDF to DOCX, but sometimes while conversion it stuck, if input file size is more then 1 MB and start utilizing 100% CPU and more memory and keep running. I want to stop this continuous thread.

1. I know stop() function is deprecated.
2. Calling thread.interrupt(); is not helping, since thread is keep running.
3. There is no loop in the code ...so cannot check for interrupted flag in loop

How to Stop a running Thread t.

public class ThreadDemo implements Runnable {

    Thread t;

    PdfToDocConversion objPdfToDocConversion;

    ThreadDemo() throws InterruptedException {

        t = new Thread(this);
        System.out.println("Executing " + t.getName());
        // this will call run() fucntion
        t.start();

        Thread.sleep(2000);

        // interrupt the threads
        if (!t.interrupted()) {
            System.out.println("Interrupted");

            t.interrupt();

        }

        System.out.println(t.isInterrupted()); // true 

        System.out.println(t.getName());

        System.out.println(t.isAlive());   /// still true 

        // block until other threads finish
        try {
            t.join();
        } catch (InterruptedException e) {
        }
    }

    public void run() {

        objPdfToDocConversion = new PdfToDocConversion();
        try {


    objPdfToDocConversion.convertDocToPdf();//inside this function thread got stuck

        } catch (InterruptedException e) {

            Thread.currentThread().interrupt(); 
            System.out.print(t.getName() + " interrupted:");
            e.printStackTrace();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static void main(String args[]) {
        try {
            new ThreadDemo();
        } catch (InterruptedException e) {
                e.printStackTrace();
        }
    }
}

Answer 1

Thread.interrupt() only sets a flag within the Thread object that the Thread should be interrupted. It does not cause the target Thread to throw an InterruptedException , instead code that can be interrupted must continually check that flag to see if someone has requested it be interrupted. That code then must handle it, usually by throwing an InterruptedException .

Answer 2

You can build your own logic in killing the thread by the help of boolean flag.

public class RunningThread implements Thread {

   private volatile boolean running = true;

   public void run() {

     while (running) {
        try {
            // Add your code here
        } catch (InterruptedException e) {
             if(!running){
                break;
             }
        }
     }
   }

   public void stopThread() {
       running = false;
       interrupt();
   }

}

Here is the usecase:

RunningThread thread = new RunningThread();
thread.start(); // start the thread
thread.stopThread(); // stops the thread

The approach above is originally used by Google developers in on of there framework aka Volley library.

Answer 3

Some of the answers say about stopping the loop with volatile boolean isRunning but I do not see any loop in your example. Interrupting the thread does not actually interrupt it "right now". It just says "thread will be interrupted as soon as there will be such an opportunity". In your case I would suggest to close your PDF file and flag it with some boolean - then you can catch the IOException and if the flag is set - it means that you caused this situation and you can finish the thread.

Answer 4

You can create a boolean field and check it inside run:

public class Task implements Runnable {

   private volatile boolean isRunning = true;

   public void run() {

     while (isRunning) {
         //do work
     }
   }

   public void kill() {
       isRunning = false;
   }

}