docs: public static String padOrTrim(String str, int num) {
      if (str == null) {
        str = "null";
      }
      int leng = str.length();
      if (leng < num) {
        StringBuilder sb = new StringBuilder(str);
        for (int i = 0; i < num - leng; i++) {
          sb.append(' ');
        }
        return sb.toString();
      } else if (leng > num) {
        return str.substring(0, num);
      } else {
        return str;
      }
    }