Observable.OnSubscribe<String> onSubscriber1 = new Observable.OnSubscribe<String>() {
  @Override
  public void call(Subscriber<? super String> subscriber) {
    subscriber.onNext("1");
    subscriber.onCompleted();
  }
};
Subscriber<String> subscriber1 = new Subscriber<String>() {
  @Override
  public void onCompleted() {

  }

  @Override
  public void onError(Throwable e) {

  }

  @Override
  public void onNext(String s) {

  }
};

Observable.create(onSubscriber1)
    .subscribe(subscriber1);

public final static <T> Observable<T> create(OnSubscribe<T> f) {
  return new Observable<T>(hook.onCreate(f));
}

protected Observable(OnSubscribe<T> f) {
  this.onSubscribe = f;
}

public final Subscription subscribe(Subscriber<? super T> subscriber) {
  return Observable.subscribe(subscriber, this);
}

private static <T> Subscription subscribe(Subscriber<? super T> subscriber, Observable<T> observable) {
  ...
  subscriber.onStart();
  hook.onSubscribeStart(observable, observable.onSubscribe).call(subscriber);
  return hook.onSubscribeReturn(subscriber);
}

public void call(Subscriber<? super String> subscriber) {
  subscriber.onNext("1");
  subscriber.onCompleted();
}

final Observable<String> memory = Observable.create(new Observable.OnSubscribe<String>() {
  @Override
  public void call(Subscriber<? super String> subscriber) {
    if (memoryCache != null) {
      subscriber.onNext(memoryCache);
    } else {
      subscriber.onCompleted();
    }
  }
});
Observable<String> disk = Observable.create(new Observable.OnSubscribe<String>() {
  @Override
  public void call(Subscriber<? super String> subscriber) {
    String cachePref = rxPreferences.getString("cache").get();
    if (!TextUtils.isEmpty(cachePref)) {
      subscriber.onNext(cachePref);
    } else {
      subscriber.onCompleted();
    }
  }
});

Observable<String> network = Observable.just("network");

//主要就是靠concat operator来实现
Observable.concat(memory, disk, network)
.first()
.subscribeOn(Schedulers.newThread())
.subscribe(s -> {
  memoryCache = "memory";
  System.out.println("--------------subscribe: " + s);
});

//拼接两个Observable的输出，不保证顺序，按照事件产生的顺序发送给订阅者
private void testMerge() {
  Observable<String> observable1 = DemoUtils.createObservable1().subscribeOn(Schedulers.newThread());
  Observable<String> observable2 = DemoUtils.createObservable2().subscribeOn(Schedulers.newThread());

  Observable.merge(observable1, observable2)
      .subscribeOn(Schedulers.newThread())
      .subscribe(System.out::println);
}

NetworkService.getToken("username", "password")
  .flatMap(s -> NetworkService.getMessage(s))
  .subscribe(s -> {
    System.out.println("message: " + s);
  });

RxView.clicks(findViewById(R.id.btn_throttle))
  .throttleFirst(1, TimeUnit.SECONDS)
  .subscribe(aVoid -> {
    System.out.println("click");
  });

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
RxSharedPreferences rxPreferences = RxSharedPreferences.create(preferences);

Preference<Boolean> checked = rxPreferences.getBoolean("checked", true);

CheckBox checkBox = (CheckBox) findViewById(R.id.cb_test);
RxCompoundButton.checkedChanges(checkBox)
    .subscribe(checked.asAction());

Observable.just("1", "2", "2", "3", "4", "5")
  .map(Integer::parseInt)
  .filter(s -> s > 1)
  .distinct()
  .take(3)
  .reduce((integer, integer2) -> integer.intValue() + integer2.intValue())
  .subscribe(System.out::println);//9