How to stop a thread created by implementing runnable interface?

Question

I have created class by implementing runnable interface and then created many threads(nearly 10) in some other class of my project.
How to stop some of those threads?

Answer 1

How to stop a thread created by implementing runnable interface?

There are many ways that you can stop a thread but all of them take specific code to do so. A typical way to stop a thread is to have a volatile boolean shutdown field that the thread checks every so often:

  // set this to true to stop the thread
  volatile boolean shutdown = false;
  ...
  public void run() {
      while (!shutdown) {
          // continue processing
      }
  }

You can also interrupt the thread which causes sleep(), wait(), and some other methods to throw InterruptedException. You also should test for the thread interrupt flag with something like:

  public void run() {
      while (!Thread.currentThread().isInterrupted()) {
          // continue processing
          try {
              Thread.sleep(1000);
          } catch (InterruptedException e) {
              // good practice
              Thread.currentThread().interrupt();
              return;
          }
      }
  }

Note that that interrupting a thread with interrupt() will not necessarily cause it to throw an exception immediately. Only if you are in a method that is interruptible will the InterruptedException be thrown.

If you want to add a shutdown() method to your class which implements Runnable, you should define your own class like:

public class MyRunnable implements Runnable {
    private volatile boolean shutdown;
    public void run() {
        while (!shutdown) {
            ...
        }
    }
    public void shutdown() {
        shutdown = true;
    }
}