val client = BaseClient()
val notificationApi = client.of[NotificationAPIV2Api]

val someHrn = "hrn:here:data::olp-here-test:whatever"
val someLayer = "whateverStreamLayer"
val result: Future[String] =
  notificationApi
    .subscribe(someHrn,
               SubscribeRequest(notificationCatalogHRN = Some(someHrn),
                                notificationStreamLayerId = Some(someLayer)))
    .executeToEntity()

result
  .andThen {
    case Success(subscriptionId) =>
      // do something with the subscription id
      println(s"${subscriptionId}")
    case Failure(ex) =>
      ex.printStackTrace()
  }

Await.result(result, Duration.Inf)

BaseClient client = BaseClientJava.instance();
NotificationAPIV2Api notificationApi = new NotificationAPIV2Api(client);

String someHrn = "hrn:here:data::olp-here-test:whatever";
String someLayer = "whateverStreamLayer";

String subscriptionId =
    notificationApi
        .subscribe()
        .withHrn(someHrn)
        .withSubscribeRequest(
            new JSubscribeRequest.Builder()
                .withNotificationCatalogHRN(someHrn)
                .withNotificationStreamLayerId(someLayer)
                .build())
        .build()
        .executeToEntity()
        .toCompletableFuture()
        .join();

// do something with the the subscription id
System.out.println(subscriptionId);