code: @Override
  	public IPv6Address toIPv6() {
  		IPAddressConverter conv = DEFAULT_ADDRESS_CONVERTER;
  		if(conv != null) {
  			return conv.toIPv6(this);
  		}
  		return null;
  	}
docs: Returns this address converted to IPv6.
  <p>
  This uses {@link #isIPv6Convertible()} to determine convertibility, and that uses an instance of {@link IPAddressConverter.DefaultAddressConverter} which uses IPv4-mapped address mappings from rfc 4038.
  <p>
  Override this method and {@link IPv6Address#isIPv4Convertible()} if you wish to map IPv4 to IPv6 according to the mappings defined by
  in {@link IPv6Address#isIPv4Compatible()}, {@link IPv6Address#isIPv4Mapped()}, {@link IPv6Address#is6To4()} or some other mapping.
  <p>
  If you override this method, you should also override the {@link IPv4Address#isIPv6Convertible()} method to match this behaviour,
  and potentially also override the reverse conversion {@link IPv6Address#toIPv4()} in your {@link IPv6Address} subclass.