code: public AtomicLong getNextIndex(String virtualHostname, boolean secure) {
          Map<String, VipIndexSupport> index = (secure) ? secureVirtualHostNameAppMap : virtualHostNameAppMap;
          return Optional.ofNullable(index.get(virtualHostname.toUpperCase(Locale.ROOT)))
                  .map(VipIndexSupport::getRoundRobinIndex)
                  .orElse(null);
      }
docs: Gets the next round-robin index for the given virtual host name. This
  index is reset after every registry fetch cycle.
  
  @param virtualHostname
  the virtual host name.
  @param secure
  indicates whether it is a secure request or a non-secure
  request.
  @return AtomicLong value representing the next round-robin index.