MultiUserChat.getJoinedRooms method return NullPointer Exception in asmack

hi,

I am really tired of this stuff know, I dont know what is the problem with my code. The single chat is working fine on my device and also if I manually enter the exact room name it is possible to join to the room and chat. Everything is working fine except I can't retreive the list of joined rooms using

MultiUserChat.getJoinedRooms(Connection, UserName);

The doc says

// Get the rooms where user3@host.org has joined

      Iterator joinedRooms = MultiUserChat.getJoinedRooms(conn, "user3@host.org/Smack");

But I am getting a null pointer exception. anybody have any idea about this.

Thanks,

Jashan