}
      for (Map.Entry<AutoCloseable, Executor> entry : entrySet()) {
        closeQuietly(entry.getKey(), entry.getValue());
      }
      clear();
      if (whenClosed != null) {
        whenClosed.countDown();
      }
    }

    void add(@Nullable AutoCloseable closeable, Executor executor) {
      checkNotNull(executor);
      if (closeable == null) {
        return;
      }