Interrupting a thread

Definition

You cannot safely force a thread to stop. Instead you ask it to stop by calling interrupt(). The thread checks isInterrupted() (or catches InterruptedException from sleep or wait) and ends itself cleanly.

Example code

Asking a worker to stop

class Demo {
    public static void main(String[] args) throws InterruptedException {
        Thread worker = new Thread(() -> {
            while (!Thread.currentThread().isInterrupted()) {       // keep working until asked to stop
                // ... do a small piece of work ...
            }
            System.out.println("worker saw the stop request and is finishing");
        });

        worker.start();
        Thread.sleep(100);
        worker.interrupt();                                         // the polite request
        worker.join();
        System.out.println("worker finished: " + !worker.isAlive());
    }
}

// Output:
// worker saw the stop request and is finishing
// worker finished: true