How can I find out if a MUC exists using Smack?

Question

Working with Smack 4.3.0 in a Multi User Chat (XEP-0045-1.21) I'm trying to find out if a room is already created or not, but I'm not sure if what I'm doing is the correct way. I have search for it and the most relative answer to it was does MUC exist?.

Technically speaking:

1. Rooms are created as public and members-only by default in OpenFire 4.2.0.
2. All room's names are an id defined by the members name in a hash string i.e. XXXXXX029d8c36b62259d0eXXXXXXXX. This means that user A can create a room with B, C and get a groupId like the previous one, but then user B (in another device) can try to create same room (with users A,B,C), which is going to give him same groupId.
3. Exist a architecture layer like whatsapp, so users can leave a Group Chat and rejoin whenever they want.
   

What I'm doing at this moment:

@WorkerThread
public boolean isGroupChatAlreadyCreated(@NonNull final String groupId)
        throws
        XmppStringprepException,
        XMPPException.XMPPErrorException,
        MultiUserChatException.NotAMucServiceException,
        SmackException.NotConnectedException,
        InterruptedException,
        SmackException.NoResponseException {
    List<HostedRoom> hostedRooms = manager.getHostedRooms(JidCreate.domainBareFrom(serviceDomain));
    for (HostedRoom hostedRoom : hostedRooms) {
        if (hostedRoom.getName().equalsIgnoreCase(groupId)) {
            return true;
        }
    }

    return false;
}

where manager is MultiUserChatManager manager and serviceDomain is just a String.

so, the questions: is this right way to do it? can it be improved?

Answer 1

I believe the easier way is get some info about room, for example its configuration form. If nothing will be returned then it means room does not exist:

public boolean isGroupChatAlreadyCreated(@NonNull final EntityBareJid groupId)
        throws
        XMPPErrorException,
        NotConnectedException,
        InterruptedException,
        NoResponseException {

    MultiUserChat multiUserChat = MultiUserChatManager.getInstanceFor(connection).getMultiUserChat(groupId);

    return multiUserChat.getConfigurationForm() != null;
}

More info here https://github.com/igniterealtime/Smack/blob/4.3/smack-extensions/src/main/java/org/jivesoftware/smackx/muc/MultiUserChat.java#L809