An API client shell that abstracts it's mechanism of executing network calls and provides a simple interface to making the calls using RxJava and Java 8.

RxApiClient.java

package me.ronshapiro.rxjavatest.app;

import java.util.concurrent.Executors;

import rx.Observable;
import rx.Observable.OnSubscribe;
import rx.Scheduler;
import rx.Subscriber;
import rx.Subscription;
import rx.android.schedulers.AndroidSchedulers;
import rx.functions.Action1;
import rx.schedulers.Schedulers;
import rx.subjects.PublishSubject;
import rx.subjects.Subject;

public class RxApiClient {

    private final Scheduler mScheduler;
    private final PublishSubject<String> mFeedSubject;
    private static final boolean ASYNC = false;
    private int counter = 0;

    public ApiClient() {
        mScheduler = Schedulers.executor(Executors.newSingleThreadExecutor());
        mFeedSubject = PublishSubject.create();
    }

    public Subscription getFeedAsync(Action1<String> action) {
        Subscription subscription = mFeedSubject.subscribe(action);
        Observable<String> feed = Observable.create((Subscriber<? super String>
                subscriber) -> {
            subscriber.onNext("emit::" + counter++);
        });
        if (ASYNC) {
            feed.subscribeOn(mScheduler)
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(mFeedSubject);
        } else {
            feed.subscribe(mFeedSubject);
        }
        return subscription;
    }

    /**
     * @param action callback to be subscribed to the subject
     * @param subject event root subject. e.x. All subscribers should listen to events published by
     * a mFeedSubject even if they created a different action
     * @param apiCallAction what to do
     * @return subscription to allow for unsubscribing
     */
    private <T> Subscription genericApiCall(Action1<T> action, Subject<T, T> subject,
            OnSubscribe<T> apiCallAction) {
        Subscription subscription = subject.subscribe(action);
        Observable<T> composition = Observable.create(apiCallAction); // rename to something better
        composition.subscribeOn(mScheduler)
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(subject);
        return subscription;
    }

    /**
     * This is all that would be necessary to add a new network call to the client.
     */
    public Subscription getFeedSimplified(Action1<String> action) {
        return genericApiCall(action, mFeedSubject, subscriber -> {
            JSONObject json = new Api().getFeed();
            List<Story> stories = parseFeed(json);
            subscriber.onNext(stories.get(i));
        });
    }
}