code: public TreeNode getChildAt(int childIndex) {
  		if (entry instanceof GroupEntry) {
  			Entry childEntry = ((GroupEntry) entry).getEntries().get(childIndex);
  			return new EntryTreeNode(this, childEntry, editors);
  		}
  		else if (entry instanceof NextCatalogEntry && childIndex == 0) {
  			try {
  				if (childCatalog == null) {
  					childCatalog = CatalogUtilities.parseDocument(((NextCatalogEntry) entry).getCatalog().toURL());
  				}
  			}
  			catch (Exception e) {
  				LOGGER.error("Exception caught trying to parse nested catalog in xml catalog", e);
  			}
  			return new CatalogTreeNode(childCatalog, editors);
  		}
  		return null;
  	}
docs: /* *********************************************
  TreeNode Interfaces