Object userObj = expandedNode.getUserObject();
if (userObj instanceof FsTreeNodeObject) {
TreeNode firstChild = expandedNode.getFirstChild();
if (firstChild instanceof DefaultMutableTreeNode
&& ((DefaultMutableTreeNode) firstChild).getUserObject() == null) {
expandedNode.removeAllChildren();
FeatureStructure fs = ((FsTreeNodeObject) userObj).getFS();
addFeatureTreeNodes(expandedNode, fs);
((JTree) event.getSource()).treeDidChange();
}