docs: public static void parseReverseLookupDomain(PtrDnsAnswer.Builder dnsAnswerBuilder, String hostname) {
  
          dnsAnswerBuilder.fullDomain(hostname);
  
          final InternetDomainName internetDomainName = InternetDomainName.from(hostname);
          if (internetDomainName.hasPublicSuffix()) {
  
              // Use Guava to extract domain name.
              final InternetDomainName topDomainName = internetDomainName.topDomainUnderRegistrySuffix();
              dnsAnswerBuilder.domain(topDomainName.toString());
          } else {
  
              /* Manually extract domain name.
               * Eg. for hostname test.some-domain.com, only some-domain.com will be extracted. */
              String[] split = hostname.split("\\.");
              if (split.length > 1) {
                  dnsAnswerBuilder.domain(split[split.length - 2] + "." + split[split.length - 1]);
              } else if (split.length == 1) {
                  dnsAnswerBuilder.domain(hostname); // Domain is a single word with no dots.
              } else {
                  dnsAnswerBuilder.domain(""); // Domain is blank.
              }
          }
      }