code: public static Inet4Address getMappedIPv4Address(Inet6Address ip) {
          if (!isMappedIPv4Address(ip))
              throw new IllegalArgumentException(String.format("Address '%s' is not IPv4-mapped.", toAddrString(ip)));
  
          return getInet4Address(copyOfRange(ip.getAddress(), 12, 16));
      }
docs: Returns the IPv4 address embedded in an IPv4 mapped address.
  
  @param ip {@link Inet6Address} to be examined for an embedded IPv4 address
  @return {@link Inet4Address} of the embedded IPv4 address
  @throws IllegalArgumentException if the argument is not a valid IPv4 mapped address