code: public Integer getNetworkPrefixLength() {
  		if(isAddress()) {
  			return parsedHost.asAddress().getNetworkPrefixLength();
  		} else if(isAddressString()) {
  			return parsedHost.asGenericAddressString().getNetworkPrefixLength();
  		}
  		return isValid() ? parsedHost.getNetworkPrefixLength() : null;
  	}
docs: If a prefix length was supplied, either as part of an address or as part of a domain (in which case the prefix applies to any resolved address),
  then returns that prefix length.  Otherwise, returns null.