Ensure that a task is interruptible

Question

How to ensure that my tasks are responsive to interruption when I call Future.cancel()?

ExecutorService executor = Executors.newSingleThreadExecutor();
Future<Boolean> future = executor.submit(task);

try {
    future.get(timeout, timeoutUnit);
} catch (TimeoutException e) {
    future.cancel(true);
}

Answer 1

How to ensure that my tasks are responsive to interruption when I call Future.cancel()?

Calling future.cancel(...) will stop the task it has not been run yet. If it is being run then if you use future.cancel(true) it will interrupt the running thread.

To stop the thread you need to test the thread interrupt flag:

if (!Thread.currentThread().isInterrupted()) {
   ...

And you need to handle handle InterruptedException appropriately. For example:

try {
    Thread.sleep(...);
} catch (InterruptedException e) {
    // re-establish the interrupt condition
    Thread.currentThread.interrupt();
    // probably stop the thread
    return;
}

See my answer about threads not interrupting.