Question

If I want to schedule at recurring task that is aligned with a specific date it would make sense to use ScheduledExecutorService. But it has no method to pass in the firstRunDate + subsequent delay to a scheduleAtFixedRate method. I know I can back out the initial delay myself but is there any reason this isn’t provided by the API? Especially as internally the SES is implemented using triggerTimes (which is what I want to pass in).

Answer 1

Based on the documentation:

All schedule methods accept relative delays and periods as arguments, not absolute times or dates. It is a simple matter to transform an absolute time represented as a Date to the required form. For example, to schedule at a certain future date, you can use: schedule(task, date.getTime() – System.currentTimeMillis(), TimeUnit.MILLISECONDS). Beware however that expiration of a relative delay need not coincide with the current Date at which the task is enabled due to network time synchronization protocols, clock drift, or other factors.

It looks as if it was a deseign decision. Its widely known that the Date class has its problems. For example TimeTask’s public void scheduleAtFixedRate(TimerTask task, Date firstTime, long period)
does not account for day light savings time.