code: public static String toLowerCase(String string, Locale locale) {
  
      if (locale == null) {
        return toLowerCase(string, STANDARD_LOCALE);
      }
      return string.toLowerCase(locale);
    }
docs: Indirection for {@link String#toLowerCase(Locale)}.
  
  @param string is the {@link String}.
  @param locale is the {@link Locale}.
  @return the result of {@link String#toLowerCase(Locale)}.