code: private void initializeSearchTextListener() {
      searchText.addListener((observable, oldText, newText) -> {
        if (newText.equals("")) { // empty search -> doesn't match anything!
          resetSearch();
        } else {
          updateSearch(newText);
        }
      });
    }
docs: Reacts upon changes in the search text.
  If the search text is empty, everything will be unmarked, else the search will be updated.