Migrate AsyncTask to RxJava

AndroidManifest.xml

    <uses-permission android:name="android.permission.INTERNET" />

build.gradle

dependencies {
    // ...
    compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
    compile 'io.reactivex.rxjava2:rxjava:2.0.1'

    compile 'com.squareup.okhttp3:okhttp:3.6.0'
}

MainActivity(After).java

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivityTAG_";
    private static final String API_URL = "http://www.mocky.io/v2/57a01bec0f0000c10d0f650f";

    private OkHttpClient client = new OkHttpClient();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        createObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<String>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                        Log.d(TAG, "onSubscribe: " + d);
                    }

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

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

                    @Override
                    public void onComplete() {
                        Log.d(TAG, "onComplete: ");
                    }
                });
    }

    private String run(String url) throws IOException {
        Request request = new Request.Builder()
                .url(url)
                .build();

        Response response = client.newCall(request).execute();
        return response.body().string();
    }

    private Observable<String> createObservable() {
        //Could use fromCallable
        return Observable.defer(new Callable<ObservableSource<? extends String>>() {
            @Override
            public ObservableSource<? extends String> call() throws Exception {
                return Observable.just(run(API_URL));
            }
        });
    }
}

MainActivity(Before).java

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivityTAG_";
    private static final String API_URL = "http://www.mocky.io/v2/57a01bec0f0000c10d0f650f";

    private OkHttpClient client = new OkHttpClient();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new MyTask().execute();
    }

    private String run(String url) throws IOException {
        Request request = new Request.Builder()
                .url(url)
                .build();

        Response response = client.newCall(request).execute();
        return response.body().string();
    }

    private class MyTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected Void doInBackground(Void... voids) {
            try {
                Log.d(TAG, "doInBackground: " + run(API_URL));
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }
    }
}