code: public String schedule(TriggerTask task) {
          if (getCurrentScheduler() == null) {
              throw new IllegalStateException("New scheduler should be crea");
          }
          ScheduledFuture<?> future = getCurrentScheduler().schedule(task.getRunnable(), task.getTrigger());
          String id = Schedulers.getUUID();
          runningSchedullers.put(id, future);
          Schedulers.increaseNoOfRunningSchedullers();
          setCurrentScheduler(null);
          return id;
      }
docs: Schedule.
  
  @param task
  the task
  @return the string