docs: public final synchronized void setPositiveList(Collection positiveList)
  	{
  		if (posList.size() == 0)
  			posList.addAll(positiveList);
  		else {
  			posList = new HashSet(positiveList);
  			// remove old keys not in the new list anymore
  			for (final Iterator i = map.keySet().iterator(); i.hasNext(); )
  				if (!posList.contains(i.next()))
  					i.remove();
  		}
  	}