docs: static private String readFile(String fileName) throws IOException {
      BufferedReader br = new BufferedReader(new FileReader(fileName));
      try {
        StringBuilder sb = new StringBuilder();
        String line = br.readLine();
  
        while (line != null) {
          sb.append(line);
          sb.append("\n");
          line = br.readLine();
        }
        return sb.toString();
      } finally {
        br.close();
      }
    }