<p>I have a String such as: </p>

<pre><code>Cerepedia, una apliación web
</code></pre>

<p>I would like to transform it into something URL valid such as: </p>

<pre><code>Cerepedia,unaaplicacionweb
</code></pre>

<p><strong>Note:</strong> the special character transformation and spaces removal. </p>

<p>By the way, are commas allowed in URLs?</p>

Have you looked at
URLEncoder
? That seems to do what you need it to do. Though the special characters will be transformed to escaped entities and not stripped from their "special" properties.