How to use Observable.fromCallable() with a checked Exception?
<p><code>Observable.fromCallable()</code> is great for converting a single function into an Observable. But how do you handle checked exceptions that might be thrown by the function?</p>

<p>Most of the examples I've seen use lambdas and "just work". But how would you do this without lambdas? For example, see the quote below from <a href="http://artemzin.com/blog/rxjava-defer-execution-of-function-via-fromcallable/">this great article</a>:</p>

<pre><code>Observable.fromCallable(() -&gt; downloadFileFromNetwork());
</code></pre>

<blockquote>
  <p>It's a one-liner now! It deals with checked exceptions, no more weird Observable.just() and Observable.error() for such easy thing as deferring code execution!</p>
</blockquote>

<p>When I attempt to implement the above Observable without a lambda expression, based on other examples I've seen, and how Android Studio auto-completes, I get the following:</p>

<pre><code>Observable.fromCallable(new Func0&lt;File&gt;() {
    @Override
    public File call() {
        return downloadFileFromNetwork();
    }
}
</code></pre>

<p>But if <code>downloadFileFromNetwork()</code> throws a checked exception, I have to try-catch it and wrap it in a <code>RuntimeException</code>. There's got to be a better way! How does the above lambda support this?!?!</p>