Filter operator on Single
<p>I start getting use to use Single instead of Observable in case that only 1 item it´s emitted, but then I realize that using Single there´s no filter operator. </p>

<p>Anybody knows an elegant way to do for instance</p>

<pre><code>      Single.just("Single use test")
            .filter(s-&gt;s.contains("test"))---&gt;How to use filter
            .map(s-&gt; s.ToUpperCase())
</code></pre>

<p>Obviously I´m trying to avoid use map or doOnNext</p>