Question

Background (can skip to question below…)

Currently working with a lego Mindstorm robot and the icommand API (http://lejos.sourceforge.net/p_technologies/nxt/icommand/api/index.html).

Having some trouble with one of the motor control methods. The methods rotates the motor by a given angle:

Motor.A.rotateTo(target);

This function will not return until the motor has completed the movement. This is fine, but sometimes the motor fails to stop and will continue indefinitely thus stopping the program.

Question

Is there anyway I can make so the program waits for up n seconds for the method Motor.A.rotateTo(target); to return. And then if it has not returned in that time, then call the method again. (If that could be looped until it is successful that would be even better.)

Thanks for reading, any help would be much appreciated.

Regards,
Joe

edit: corrected from Motor.A.rotate(target); to Motor.A.rotateTo(target);

Answer 1

You can use ExecutorService or other threading solution to run rotate in a separate thread and wait for results. Here is a complete program that also retries given number of times:

public static void main(String[] args) throws TimeoutException {
    final ExecutorService pool = Executors.newFixedThreadPool(10);
    runWithRetry(pool, 5);  //run here
}

public static void runWithRetry(final ExecutorService pool, final int retries) throws TimeoutException {
        final Future<?> result = pool.submit(new Runnable() {
            @Override
            public void run() {
                Motor.A.rotate(angle);
            }
        });
        try {
            result.get(1, TimeUnit.SECONDS);  //wait here
        } catch (InterruptedException e) {
            throw new RuntimeException(e.getCause());
        } catch (ExecutionException e) {
            throw new RuntimeException(e.getCause());
        } catch (TimeoutException e) {
            if (retries > 1) {
                runWithRetry(pool, retries - 1);  //retry here
            } else {
                throw e;
        }
    }
}