code: public RosterGroup createGroup(String name) {
          final XMPPConnection connection = connection();
          if (groups.containsKey(name)) {
              return groups.get(name);
          }
  
          RosterGroup group = new RosterGroup(name, connection);
          groups.put(name, group);
          return group;
      }
docs: Creates a new group.
  <p>
  Note: you must add at least one entry to the group for the group to be kept
  after a logout/login. This is due to the way that XMPP stores group information.
  </p>
  
  @param name the name of the group.
  @return a new group, or null if the group already exists