public static void scheduleWithFixedDelay(ScheduledExecutorService exec, Duration delay, Callable<Signal> callable)
  {
    scheduleWithFixedDelay(exec, delay, delay, callable);
  }
public static void scheduleWithFixedDelay ( ScheduledExecutorService exec , Duration delay , Callable < Signal > callable ) { scheduleWithFixedDelay ( exec , delay , delay , callable ) ; }
Run callable repeatedly with the given delay between calls, after the given
initial delay, until it returns Signal.STOP. Exceptions are caught and
logged as errors.