title: RxJava introduced Single<T>. How do I convert an Observable<T> to a Single<T>?
body: <p>RxJava recently introduced <a href="http://reactivex.io/documentation/single.html" rel="noreferrer">Single</a>. Is there a way to convert an already existing Observable (that's pretty much a Single) to a Single without modifying the source of the original observable?</p>
  
  <p>For example, I have an api service class with a method that returns an Observable - which is essentially fetching a User from a remote resource. Say I can't modify the service. I want to consume this elsewhere but return a Single. How do I do this?</p>
  
  <p><strong>A pinch more background</strong> </p>
  
  <p>RxJava recently introduced the concept of a Single which is more or less an Rx friendly simple callback (i.e. an Observable emitting one object or an error) (read more about it here - <a href="http://reactivex.io/documentation/single.html" rel="noreferrer">http://reactivex.io/documentation/single.html</a>)</p>