code: public static String lowerCase(String str) {
          if(isNullOrEmpty(str)) {
              return str;
          }
          return str.toLowerCase(LOCALE_ENGLISH);
      }
docs: Converts a given String to lower case with Locale.ENGLISH
  
  @param str the string to be converted to lower case
  @return the lower case of string, or itself if string is null/empty