*
   * @param ip {@link Inet6Address} to be examined for 6to4 address format
   * @return {@code true} if the argument is a 6to4 address
   */
  public static boolean is6to4Address(Inet6Address ip) {
    byte[] bytes = ip.getAddress();
    return (bytes[0] == (byte) 0x20) && (bytes[1] == (byte) 0x02);
  }

  /**
   * Returns the IPv4 address embedded in a 6to4 address.
   *

    for (String non6to4Address : non6to4Addresses) {
      InetAddress ip = InetAddresses.forString(non6to4Address);
      assertFalse(InetAddresses.is6to4Address((Inet6Address) ip));
      assertThrows(
          "IllegalArgumentException expected for '" + non6to4Address + "'",
          IllegalArgumentException.class,