code: public void add(final GridmixJob job) throws InterruptedException {
      final boolean addToQueue = !shutdown;
      if (addToQueue) {
        final SubmitTask task = new SubmitTask(job);
        sem.acquire();
        try {
          sched.execute(task);
        } catch (RejectedExecutionException e) {
          sem.release();
        }
      }
    }
docs: Enqueue the job to be submitted per the deadline associated with it.