Retrofit bug

RxJava.java

public class RxJava {

    public static void main(String[] args) {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://google.com/")
                .addCallAdapterFactory(RxJavaCallAdapterFactory.createAsync())
                .build();

        Service service = retrofit.create(Service.class);

        Subscription subscription = service.dummyApiCall()
                .toSingle()
                .subscribe(new Observer<Response<Void>>() {
                    @Override
                    public void onCompleted() {
                        System.out.println("Complete");
                    }

                    @Override
                    public void onError(Throwable throwable) {
                        throwable.printStackTrace();
                    }

                    @Override
                    public void onNext(Response<Void> voidResponse) {
                        System.out.println(voidResponse.code());
                    }
                });
    }

    public interface Service {
        @GET("/")
        Observable<Response<Void>> dummyApiCall();
    }
}