title: Nice general way to sort nulls to the bottom, regardless?
body: <p>I'm writing some custom Comparators, and I'd like them to push null items to the bottom of the list, regardless of whether I'm sorting ascending or descending.  What's a good strategy or pattern for approaching this? </p>
  
  <p>Offhand: </p>
  
  <ul>
  <li>Simply write separate ascending and
  descending comparators, sharing code
  where possible</li>
  <li>Delegate null handling to another
  class, either by throwing an NPE or
  by calling it explicitly</li>
  <li>Include an ascending flag and put
  conditional logic in it to navigate
  around the nulls</li>
  <li>Wrap regular comparators in a
  null-handling class</li>
  </ul>
  
  <p>Any other strategies?  I'd like to hear about any experiences with different approaches, and any pitfalls for the various strategies.</p>