How do you refresh the token?

[ihrthk]

public Observable<T> get(String keyToken, Class<T> classToken) {
        T response = retrieve(keyToken, classToken);

        if (response != null) {
            if (response instanceof OAuth2AccessToken) {
                if (!((OAuth2AccessToken)response).isExpired()) {
                    return Observable.just(response);
                }
            } else {
                return Observable.just(response);
            }
        }

        return null;
    }

[VictorAlbertos]

When the token is expired a null value is returned. So, the calling method knows that way that it is required to ask for a new token.