Trying to read cloudstorage.properties. Getting NullPointerException

Question

I have a problem using the Google Cloud Storage in my app, basically where I'm failing is retrieving the GoogleCredential from this line, that is giving me a NullPointerException =

GoogleCredential credential = new GoogleCredential.Builder()

I'm trying to get the Google Application Default Credentials, but I don´t have to a Google Compute Engine, I would prefer using Google App Engine.

I'm using that line of code for making this method that is the responsable for the uploading and downloading the file =

private static Storage getStorage() {
        if (storage == null) {
            HttpTransport httpTransport = new NetHttpTransport();
            JsonFactory jsonFactory = new JacksonFactory();

            List<String> scopes = new ArrayList<>();
            scopes.add(StorageScopes.DEVSTORAGE_FULL_CONTROL);

            try {
                GoogleCredential credential = new GoogleCredential.Builder()
                        .setTransport(httpTransport)
                        .setJsonFactory(jsonFactory)
                        .setServiceAccountId(
                                getProperties().getProperty(ACCOUNT_ID_PROPERTY))
                        .setServiceAccountPrivateKeyFromP12File(
                                new File(getProperties().getProperty(
                                        PRIVATE_KEY_PATH_PROPERTY)))
                        .setServiceAccountScopes(scopes).build();

                storage = new Storage.Builder(httpTransport, jsonFactory,
                        credential).setApplicationName(
                        getProperties().getProperty(APPLICATION_NAME_PROPERTY))
                        .build();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return storage;
    }

to add more into the question, after debugging I noticed that the line that is giving me the nullPointerException is in this method =

private static Properties getProperties() throws Exception {

        if (properties == null) {
            properties = new Properties();
            InputStream stream = CloudStorage.class
                    .getResourceAsStream("/cloudstorage.properties");
            try {
                properties.load(stream);
            } catch (IOException e) {
                throw new RuntimeException(
                        "cloudstorage.properties must be present in classpath",
                        e);
            } finally {
                stream.close();
            }
        }
        return properties;
    }

specifically this line of code =

InputStream stream = CloudStorage.class
                        .getResourceAsStream("/cloudstorage.properties");