code: public synchronized void stop() {
          if (!started) {
              return;
          }
          try {
              if (future != null) {
                  future.cancel(true);
                  future = null;
              }
              if (scheduledExecutorService != null) {
                  scheduledExecutorService.shutdownNow();
                  scheduledExecutorService = null;
              }
          } catch (Throwable t) {
              LOGGER.warn(t.getMessage(), t);
          } finally {
              SCHEDULED_SERVICE_MAP.remove(this);
              started = false;
          }
      }
docs: 停止执行定时任务，还可以重新start