Storing a list to another list
<p>If I had the following declaration of the list:</p>

<pre><code>List&lt; Integer&gt; b = new ArrayList&lt; Integer&gt;();
</code></pre>

<p>and</p>

<pre><code>List&lt; HashSet &lt; Integer&gt;&gt; c = new ArrayList&lt; HashSet&lt; Integer&gt;&gt;();
</code></pre>

<p>I was wondering how would I be able to add <code>b</code> to <code>c</code>?</p>

<p>I've tried <code>c.add(b);</code> 
but this doesn't work.</p>

<p>Thanks for any help!</p>
