code: public static ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
          return getInstance().executorService.schedule(command, delay, unit);
      }
docs: @see java.util.concurrent.ScheduledExecutorService
  
  @param command the task to execute
  @param delay the time from now to delay execution
  @param unit the time unit of the delay parameter
  @return a ScheduledFuture representing pending completion of the task and whose {@code get()} method will return {@code null} upon completion
  @throws RejectedExecutionException if the task cannot be scheduled for execution