public Collection<JID> getMembers() {
        return Collections.unmodifiableMap(members).keySet();
    }
Returns a collection with the current list of room members. The collection contains the
bareJID of the users with member affiliation. If the room is not members-only then the list
will contain the users that registered with the room and therefore they may have reserved a
nickname.

@return a collection with the current list of members.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/MUCRoom.java