code: public static <T> void addExceptionCallback(ListenableFuture<T> future, Runnable exceptionCallback, Executor executor)
      {
          requireNonNull(exceptionCallback, "exceptionCallback is null");
  
          addExceptionCallback(future, t -> exceptionCallback.run(), executor);
      }
docs: Invokes the callback, using the specified executor, if the future fails.