private class ObserverState implements Observer {
    @Override
    public void update(Observable observable, Object o) {
        if (o instanceof UFService.SharedEvent) {
            ...
        }
    }
 }

DdiRestApi api = new ClientBuilder()
            .withBaseUrl("https://personal.updatefactory.io")
            .withGatewayToken("[gatewayToken]")
            .withHttpBuilder(new OkHttpClient.Builder())
            .withOnTargetTokenFound(System.out::println)
            .withServerType(ServerType.UPDATE_FACTORY)
            .build();

Map<String,String> map = new HashMap<>();
map.put("test","tes");

ufService = UFService.builder()
            .withClient(api)
            .withControllerId("controllerId")
            .withTargetData(()->map)
            .withTenant("test")
            .build();

ufService.addObserver(new ObserverState());

ufService.start();