title: How to chain two Completable in RxJava2
body: <p>I have two Completable. I would like to do following scenario:
  If first Completable gets to onComplete , continue with second Completable. The final results would be onComplete of second Completable.</p>
  
  <p>This is how I do it when I have Single <strong>getUserIdAlreadySavedInDevice()</strong> and Completable <strong>login()</strong>:</p>
  
  <pre><code>@Override
  public Completable loginUserThatIsAlreadySavedInDevice(String password) {
      return getUserIdAlreadySavedInDevice()
              .flatMapCompletable(s -&gt; login(password, s))
  
  }
  </code></pre>