code: public static UnaryOperator<String> toLowerCase(final Locale locale) {
      return  new UnaryOperator<String>() {
        @Override public String apply(String s) {
          return s.toLowerCase(locale);
        }
        @Override public String toString() {
          return "toLowerCase";
        }
      };
    }
docs: Returns a {@link UnaryOperator} that maps a {@link String} to lower case using {@code locale}.