@JsonIgnore public static void getUser(String uid, RibbitValueListener<UserWrapper> valueListener) { if ((uid != null) && (uid.length() != mCurrentUser.getId().length())) { throw new IllegalStateException("requested user id not valid : " + uid); } Firebase firebase = RibbitUser.getFirebaseUsers().child("/" + uid); firebase.addListenerForSingleValueEvent(new UserValueListener(valueListener)); }