还是树的问题（编译成功，运行出错！）

首先感谢"傻傻猪"先生,中午帮我解决了一个问题。
我修改了代码后，想在树中添加一个节点，程序编译成功了，但运行时节点没有加进去，不知是何原因？
部分代码为：
                      ......
                    int id=Integer.parseInt(tempID);
                         if(id<1 || id>tempNode.getChildCount()+1) 
                         {
                             JOptionPane.showMessageDialog(Sample25_2.this,"输入数字太大或太小!","错误",
                                     JOptionPane.WARNING_MESSAGE);
                                return;
                         } 
                         DefaultMutableTreeNode newNode=new DefaultMutableTreeNode(tempName);
                         newNode.insert(newNode, id-1);
                         ((DefaultTreeModel)jt.getModel()).reload(tempNode);
                         jt.setExpandsSelectedPaths(true);
                         jtf.setText("您在"+tempNode+"中添加了"+newNode+"节点!");
                         ......  运行时提示如下：  Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: new child is an ancestor
        at javax.swing.tree.DefaultMutableTreeNode.insert(DefaultMutableTreeNode.java:165)
        at javaapplication10.Sample25_2$MyToolBarButtonListener.actionPerformed(Main.java:128)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButto
n$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:6038)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5803)
        at java.awt.Container.processEvent(Container.java:2058)
        at java.awt.Component.dispatchEventImpl(Component.java:4410)
        at java.awt.Container.dispatchEventImpl(Container.java:2116)
        at java.awt.Component.dispatchEvent(Component.java:4240)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
        at java.awt.Container.dispatchEventImpl(Container.java:2102)
        at java.awt.Window.dispatchEventImpl(Window.java:2429)
        at java.awt.Component.dispatchEvent(Component.java:4240)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)