@Nullable
    MUCRoom get(@Nonnull final String roomName)
    {
        return ROOM_CACHE.get(roomName);
    }
Retrieve a specific room, if one is currently managed by this instance.

Note that when obtaining a room instance using this method, the caller should take responsibility to make sure
that any changes to the instance will become visible to other cluster nodes (which is done by invoking
{@link #sync(MUCRoom)}. Where appropriate, the caller should apply mutex (as returned by {@link #getLock(String)})
to control concurrent access to the returned instance.

@param roomName The name of the room to retrieve.
@return The room
xmppserver/src/main/java/org/jivesoftware/openfire/muc/spi/LocalMUCRoomManager.java