title: ConcurrentSkipListMap sorting: Can it be done by the value's compareTo?
body: <p>In a game, I'm trying to keep a list of users and have it sorted by score, so that I could query the list at any given time and return (for example) the top ten users by score.  This list should be thread-safe.  I envision using the userName string as a key and the value would be a User object which implements Comparable and has properties such as displayName and score.  The User object would therefore have a compareTo method which would compare the score attribute to determine its position.  </p>
  
  <p>I'm looking at using a ConcurrentSkipListMap for this, but as best I can tell, the Map (as opposed to the Set) uses the key to sort.  I'd like to have the list sorted by the score property of the User object, but still use a Map because I need to be able access any given user and modify their score attribute from a thread.  </p>
  
  <p>It doesn't seem that using my own Comparator for the key would solve my problem, as I doubt I'd have access to the associated value for comparison.  I could use a ConcurrentSkipListSet but accessing the list to modify an individual user's score would be (I would imagine) an expensive operation (due to the need to iterate every time).  </p>
  
  <p>Would anyone be able to suggest how to accomplish this? </p>