code: public static String getNodeVersionByJid(Jid jid) {
          NodeVerHash nvh = JID_TO_NODEVER_CACHE.lookup(jid);
          if (nvh != null) {
              return nvh.nodeVer;
          } else {
              return null;
          }
      }
docs: Get the Node version (node#ver) of a JID. Returns a String or null if
  EntiyCapsManager does not have any information.
  
  @param jid
  the user (Full JID)
  @return the node version (node#ver) or null