private static void formatString(List<String>[] strings, int index, StringBuilder out) {
    out.append(strings[0].get(index));
    for (int i = 1; i < strings.length; i++) {
      out.append(',');
      List<String> list = strings[i];
      out.append(list.size() > index ? list.get(index) : "");
    }
  }
private static void formatString(List<String>[] strings, int index, StringBuilder out)