Chained Api calls with RxJava

Example.java

public class Example {

    private String auth_token;

    private void chainApiCalls() throws Exception {
        api.getToken()
           .doOnNext(token -> auth_token = token)
           .flatMap(api::getPersonNumber)
           .flatMap(person_number -> api.getUserInfo(auth_token, person_number))
           .doOnCompleted(() -> auth_token = null)
           .subscribe(userInfo -> {
               // do something with userInfo here...
           });
    }

    interface Api {

        Observable<String> getToken();

        Observable<PersonNumber> getPersonNumber(String token);

        Observable<UserInfo> getUserInfo(String token, PersonNumber person);

        class UserInfo {
        }

        class PersonNumber {
        }
    }

    Api api = new Api() {
        @Override public Observable<String> getToken() { return null; }

        @Override public Observable<PersonNumber> getPersonNumber(String token) { return null; }

        @Override public Observable<UserInfo> getUserInfo(String token, PersonNumber person) {
            return null;
        }
    };

}