Question

Consider I scheduled a Runnable for periodic execution with ScheduledExecutorService and there occurs some system Error like OutOfMemory. It will be silently swallowed.

scheduler.scheduleWithFixedDelay(new Runnable() {
                    @Override
                    public void run() {
                      throw new OutOfMemoryError(); // Swallowed
                    }
                }, 0, delay, TimeUnit.SECONDS);

Is it normal?

Why doesn’t it propagate to the container?

What is the correct way to handle such errors?

Thanks!

Answer 1

An OutOfMemoryError, like any subtype of Error, cannot be recovered from, they’re generally fatal to your program. It doesn’t really matter if you try and catch it or not, your program’s going down.

If, however, you mean an Exception rather than an Error, then you have 2 options:

1. Catch the exception from within your task’s run() method.
2. Call get() on the Future() returned by scheduleWithFixedDelay(). This will propagate the exception back to the submitting thread, but it will block until that happens.