title: Is there an insertion order preserving Set that also implements List?
body: <p>I'm trying to find an implementation of <code>java.util.List</code> and <code>java.util.Set</code> at the same time in Java. I want this class to allow only unique elements (as <code>Set</code>) and preserve their order (like <code>List</code>). Does it exist in JDK 6?</p>
  
  <p>It's important to have <code>List&lt;T&gt;#add(int, T)</code> so I can insert into a specific position.</p>