code: public void put(Resource resource, Resource.Iterator iterator) {
  
  		assert (resource != null);
  
  		Integer key = Integer.valueOf(System.identityHashCode(resource));
  		if (iterator != null) {
  			map.put(key, iterator);
  		} else {
  			map.remove(key);
  		}
  	}
docs: Associate the iterator to the given resource. If the iterator is null,
  then the mapping is removed.
  
  @param resource
  resource to associate the iterator to
  @param iterator
  iterator to associate to the resource; if null mapping is
  removed