code: public static Inet4Address get6to4IPv4Address(Inet6Address ip) {
      Preconditions.checkArgument(is6to4Address(ip),
          "Address '%s' is not a 6to4 address.", toAddrString(ip));
  
      return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 2, 6));
    }
docs: Returns the IPv4 address embedded in a 6to4 address.
  
  @param ip {@link Inet6Address} to be examined for embedded IPv4 in 6to4 address
  @return {@link Inet4Address} of embedded IPv4 in 6to4 address
  @throws IllegalArgumentException if the argument is not a valid IPv6 6to4 address