Swing中tree的问题

Question

addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent e){
selectedNode=(DefaultMutableTreeNode)
                   effectiveTree.getLastSelectedPathComponent();
if(selectedNode==null) return;
DefaultMutableTreeNode newNode=new DefaultMutableTreeNode
                   ("待编辑节点");
model.insertNodeInto
                (newNode,selectedNode,selectedNode.getChildCount());
TreeNode[] nodes=model.getPathToRoot(newNode);
TreePath paths=new TreePath(nodes);
effectiveTree.scrollPathToVisible(paths);
      }
}