docs: private String readFile(String fileName) {
          String text;
          try {
              try (Reader r = new FileReader(fileName)) {
                  text = Kit.readReader(r);
              }
          } catch (IOException ex) {
              MessageDialogWrapper.showMessageDialog(this,
                                                     ex.getMessage(),
                                                     "Error reading "+fileName,
                                                     JOptionPane.ERROR_MESSAGE);
              text = null;
          }
          return text;
      }