Would like to avoid duplicate entries in a ArrayList
<p>I am looking for an object like ArrayList that would let me avoid duplicate entries.
For example it might have a method that calls 'contains()' to valid each entry before it is added to the ArrayList.</p>

<pre><code>ArrayList&lt;String&gt; al = new ArrayList&lt;String&gt;();
if(!al.contains("red")){
  al.add("red");
}
</code></pre>

<p>Does something like this exist?</p>
