RetrofitFragment Rx demo

GithubService.java

public class GithubService {

    private GithubService() { }

    public static GithubApi createGithubService(final String githubToken) {
        Retrofit.Builder builder = new Retrofit.Builder().addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl("https://api.github.com");

        if (!TextUtils.isEmpty(githubToken)) {

            OkHttpClient client = new OkHttpClient.Builder().addInterceptor(new Interceptor() {
                @Override public Response intercept(Chain chain) throws IOException {
                    Request request = chain.request();
                    Request newReq = request.newBuilder()
                            .addHeader("Authorization", format("token %s", githubToken))
                            .build();
                    return chain.proceed(newReq);
                }
            }).build();

            builder.client(client);
        }

        return builder.build().create(GithubApi.class);
    }
}

RetrofitFragment.java

    @OnClick(R.id.btn_demo_retrofit_contributors_with_user_info)
    public void onListContributorsWithFullUserInfoClicked() {
        _adapter.clear();

        _subscriptions.add(_githubService.contributors(_username.getText().toString(), _repo.getText().toString())
              .flatMap(new Func1<List<Contributor>, Observable<Contributor>>() {
                  @Override
                  public Observable<Contributor> call(List<Contributor> contributors) {
                      return Observable.from(contributors);
                  }
              })
              .flatMap(new Func1<Contributor, Observable<Pair<User, Contributor>>>() {
                  @Override
                  public Observable<Pair<User, Contributor>> call(Contributor contributor) {
                      Observable<User> _userObservable = _githubService.user(contributor.login)
                            .filter(new Func1<User, Boolean>() {
                                @Override
                                public Boolean call(User user) {
                                    return !isEmpty(user.name) && !isEmpty(user.email);
                                }
                            });

                      return Observable.zip(_userObservable,
                            Observable.just(contributor),
                            new Func2<User, Contributor, Pair<User, Contributor>>() {
                                @Override
                                public Pair<User, Contributor> call(User user, Contributor contributor) {
                                    return new Pair<>(user, contributor);
                                }
                            });
                  }
              })
              .subscribeOn(Schedulers.newThread())
              .observeOn(AndroidSchedulers.mainThread())
              .subscribe(new Observer<Pair<User, Contributor>>() {
                  @Override
                  public void onCompleted() {
                      Timber.d("Retrofit call 2 completed ");
                  }

                  @Override
                  public void onError(Throwable e) {
                      Timber.e(e, "error while getting the list of contributors along with full " + "names");
                  }

                  @Override
                  public void onNext(Pair<User, Contributor> pair) {
                      User user = pair.first;
                      Contributor contributor = pair.second;

                      _adapter.add(format("%s(%s) has made %d contributions to %s",
                            user.name,
                            user.email,
                            contributor.contributions,
                            _repo.getText().toString()));

                      _adapter.notifyDataSetChanged();

                      Timber.d("%s(%s) has made %d contributions to %s",
                            user.name,
                            user.email,
                            contributor.contributions,
                            _repo.getText().toString());
                  }
              }));
    }