public long getNonPersistentRoomCount() {
        final Lock lock = ROOM_CACHE_STATS.getLock(STAT_KEY_ROOMCOUNT_NONPERSISTENT);
        lock.lock();
        try {
            return ROOM_CACHE_STATS.getOrDefault(STAT_KEY_ROOMCOUNT_NONPERSISTENT, 0L);
        } finally {
            lock.unlock();
        }
    }
Returns a count of all rooms that are non-persistent.

The statistic returned by this method is based on a derived value. It is not based on a direct re-evaluation of
each room.

This method is not as resource intensive, but perhaps less accurate, than {@link #recomputeNonPersistentRoomCount()}.

@return The count of non-persistent MUC rooms.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/spi/LocalMUCRoomManager.java