Review

class FilterManager.FilterCleaner {
    public void run () {
      while (running) {

        // sort items from oldest to newest 
        // we delete the oldest filters 
        if (cache.size() > cacheCleanSize) {
          // empty the temporary set
          sortedFilterItems.clear();
          synchronized (cache) {
            sortedFilterItems.addAll(cache.entrySet());
            Iterator it = sortedFilterItems.iterator();
            int numToDelete = (int) ((cache.size() - cacheCleanSize) * 1.5);
            int counter = 0;
            // loop over the set and delete all of the cache entries not used in a while
            while (it.hasNext() && counter++ < numToDelete) {
              Map.Entry entry = (Map.Entry)it.next();
              cache.remove(entry.getKey());
            }
          }
          // empty the set so we don't tie up the memory
          sortedFilterItems.clear();
        }
        // take a nap
        try {
          Thread.sleep(cleanSleepTime);
        } catch (InterruptedException ie) {
          Thread.currentThread().interrupt();
          throw new RuntimeException(ie);
        }
      }
    }

}