getByIdSync.java

public ChatRoom getById(String id) {
    ApiFuture<DocumentSnapshot> chatRoomSnapshotFuture =
            firestore.collection(ServiceConstants.CHAT_ROOMS).document(id).get();
    try {
        DocumentSnapshot chatRoomSnapshot = chatRoomSnapshotFuture.get();
        return new ChatRoom(chatRoomSnapshot.getId(), chatRoomSnapshot.getString("name"));
    } catch (Exception e) {
        throw new RuntimeException("Could not retrieve by id", e);
    }
}