*
   * @throws NumberFormatException if the string does not contain a valid unsigned {@code byte}
   *     value
   * @throws NullPointerException if {@code string} is null (in contrast to {@link
   *     Byte#parseByte(String)})
   * @since 13.0
   */
  @CanIgnoreReturnValue
  public static byte parseUnsignedByte(String string) {
    return parseUnsignedByte(string, 10);
  }

  /**

    @Test
    public void test_parseDate() {
        Date date;

        date = FessFunctions.parseDate("");
        assertNull(date);

        date = FessFunctions.parseDate("2004-04-01T12:34:56.123Z");
        assertEquals("2004-04-01T12:34:56.123Z", FessFunctions.formatDate(date));

        date = FessFunctions.parseDate("2004-04-01T12:34:56Z");
        assertEquals("2004-04-01T12:34:56.000Z", FessFunctions.formatDate(date));

                    return !validateDateTimeString(source.get(s));
                }).collect(Collectors.toList()));
    }

    default boolean validateDateTimeString(final Object obj) {
        if (FessFunctions.parseDate(obj.toString()) != null) {
            return true;
        }
        return false;
    }

    String getIndexAdminIntegerFields();

    default Set<String> getIndexAdminIntegerFieldSet() {