RxJava introduced Single<T>. How do I convert an Observable<T> to a Single<T>?

Question

RxJava recently introduced Single. 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?

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?

A pinch more background

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 - http://reactivex.io/documentation/single.html)

Answer 1

I think another answer is outdated. You should probably check the following methods.

singleOrError: Emits the one and only element, IndexOutOfBoundsException if the source is longer than 1 item or a NoSuchElementException if the source is empty.

firstOrError: Emits the first element or a NoSuchElementException if the source is empty.

lastOrError: Emits the lastelement or a NoSuchElementException if the source is empty.

elementAtOrError: Emits the indexth element or a NoSuchElementException.

More info on this page: https://github.com/ReactiveX/RxJava/wiki/What%27s-different-in-2.0