@Override
  public String toString() {
    return super.toString();
  }

  /**
   * Returns the Java Unicode escape sequence for the given {@code char}, in the form "\u12AB" where
   * "12AB" is the four hexadecimal digits representing the 16-bit code unit.
   */
  private static String showCharacter(char c) {
    String hex = "0123456789ABCDEF";
    char[] tmp = {'\\', 'u', '\0', '\0', '\0', '\0'};

  @Override
  public String toString() {
    return super.toString();
  }

  /**
   * Returns the Java Unicode escape sequence for the given {@code char}, in the form "\u12AB" where
   * "12AB" is the four hexadecimal digits representing the 16-bit code unit.
   */
  private static String showCharacter(char c) {
    String hex = "0123456789ABCDEF";
    char[] tmp = {'\\', 'u', '\0', '\0', '\0', '\0'};

      "Invalid URL host: \"[0:0:0:0:0:1:0.0.0.000001]\"",
    )
  }

  @Test
  fun hostIpv6WithIpv4SuffixWithHexadecimalPrefix() {
    // Chrome interprets a leading '0x' as hexadecimal; Firefox rejects them. (We reject them.)
    assertInvalid(
      "http://[0:0:0:0:0:1:0.0x10.0.0x10]/",
      "Invalid URL host: \"[0:0:0:0:0:1:0.0x10.0.0x10]\"",
    )
  }

  @Test