title: Observable which does not pass anything in onNext()
body: <p>I would need an Observable, for example to provide a system clock, which does not need to pass anything in onNext(). I couldn't find a signature that would allow me to do that.</p>
  
  <p>Sure, I could use any object and then pass null, but that doesn't make much sense. So my question is if there is a better way to do that.</p>
  
  <pre><code>Observable.create(new Observable.OnSubscribe&lt;Anyobject&gt;() { // use any object in the signature
  
              @Override public void call(Subscriber&lt;? super Anyobject&gt; subscriber) {
  
                      subscriber.onNext(null); // then pass null
                      subscriber.onCompleted();
  
              }
  
          })
  </code></pre>