private void tellPageWasRead(long pageNumber, Page page) {
    ApplicationManager.getApplication().invokeLater(() -> {
      if (page == null) {
        LOG.warn("page with number " + pageNumber + " is null.");
        return;
      }

      pagesCache.add(page);
      numbersOfRequestedForReadingPages.remove(pageNumber);
      requestUpdate();
    });
  }
private void tellPageWasRead(long pageNumber, Page page)