how to get joined groupInfo & their member info using XMPP?

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http://stackoverflow.com – To get Joined Room List i have tried:, Iterator<String> rooms = MultiUserChat.getJoinedRooms(conn, userJID); //System.out.println("ROOM:"+rooms); while (rooms.hasNext()) { System.out.println("Room list: "+new DiscoverItems.Item(rooms.next()).toString());; } but, it gives NPE. So how can i fetch joined group List? There is 1 joined group where 3 members are participants on my server Side. To get RoomInfo i have tried: RoomInfo info = null; try { info = MultiUserChat.getRoomInfo(conn,chatRoomName); } catch (XMPPException e) { // TOD (HowTos)