code: public static String getHostnameValue() {
          if (!hostnameInitialised) {
              synchronized (LOCK) {
                  if (!hostnameInitialised) {
                      hostname = lookupHostname();
                      hostnameInitialised = true;
                  }
              }
          }
          return hostname;
      }
docs: Memoises the hostname, as lookup can be expensive