Remove Duplicates from ArrayList<ArrayList<String>> Object
<p>I have an ArrayList that has a nested ArrayList of Strings and I want to remove duplicates from.  I know if I always wanted to remove duplicates, I shouldn't use an ArrayList, but in some cases duplicates are valid.  What is the best way to remove duplicates from the nested ArrayList?</p>

<p><strong>For example, I would like to execute some Java that converts:</strong></p>

<pre><code>[[duplicate], [duplicate], [duplicate], [unique1], [unique2]]
</code></pre>

<p><strong>to:</strong></p>

<pre><code>[[duplicate], [unique1], [unique2]]
</code></pre>
