code: public static int activeCount() {
          int activeCount = 0;
          for (ExecutorService pool : EXECUTORS) {
              if (pool instanceof ThreadPoolExecutor) {
                  activeCount += ((ThreadPoolExecutor) pool).getActiveCount();
              }
          }
          for (ExecutorService pool : EXPLICIT_EXECUTORS) {
              if (pool instanceof ThreadPoolExecutor) {
                  activeCount += ((ThreadPoolExecutor) pool).getActiveCount();
              }
          }
          return activeCount;
      }
docs: 监控api