code: public static ScheduledExecutorService newScheduledExecutor(int corePoolSize) {
          ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(corePoolSize);
          EXECUTORS.add(scheduledExecutorService);
          return scheduledExecutorService;
      }
docs: create a new xian monitored scheduled thread pool
  
  @param corePoolSize the core pool size
  @return the newly created thread pool