for(Iterator iter = groupModels.iterator(); iter.hasNext();)
GroupModel[] models = groupingMethod.getGroups(); for(int i=0;i<models.length;i++)
    public void clearThumbnails()    {        thumbnailSet.clear();        for(Iterator iter = groupModels.iterator(); iter.hasNext();)        {            GroupModel group = (GroupModel)iter.next();            group.clearThumbnails();        }        updateModelListeners();    }