asynchronous in Rxjava

async rx.java

// sample 2 asynchronous task
Observable<String> jsonTask = Observable.create(new Observable.OnSubscribe<String>() {
    @Override
    public void call(Subscriber<? super String> subscriber) {
        subscriber.onNext(getJsonFromInternet());
        subscriber.onCompleted();
    }
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());

// SUBCRIBE
jsonTask.subscribe(new Subscriber<String>() {
    @Override
    public void onCompleted() {
        Log.d(TAG, "onCompleted: ");
    }

    @Override
    public void onError(Throwable e) {
        Log.d(TAG, "onError: " + e.getMessage());
    }

    @Override
    public void onNext(String s) {
        Log.d(TAG, "onNext: " + s);
    }
});

private String getJsonFromInternet() {
        HttpURLConnection connection = null;
        try {
            URL url = new URL("http://api.androidhive.info/contacts/");
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(5000);
            connection.connect();

//            if(connection.getResponseCode() == 200){
//
//            }
            BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            StringBuilder sb = new StringBuilder();
            String line;
            while ((line = br.readLine()) != null) {
                sb.append(line + "\n");
            }
            br.close();
            return sb.toString();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }