这么简单的问题难道没人知道吗？从JTree删除或增加一个节点后，如何更新显示？

以下是我删除节点的代码：    public void jTree1_valueChanged(TreeSelectionEvent e) {
        DefaultMutableTreeNode selNode = (DefaultMutableTreeNode)jTree1.getLastSelectedPathComponent();
        TreeNode selRoot = selNode.getParent();
        selNode.removeFromParent();
    }我尝试了validate(),inValidate()都不行，有人说用revalidate,repaint,也不行，也有人说用updateUI()，但是这个方法显然不对，这个方法由UIManager调用，用于发出L&F已经更改的通知，并且如果手动调用将发生异常，以下是异常信息：Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.basic.BasicTreeUI.isToggleEvent(BasicTreeUI.java:2192)
at javax.swing.plaf.basic.BasicTreeUI.selectPathForEvent(BasicTreeUI.java:2257)
at javax.swing.plaf.basic.BasicTreeUI$Handler.handleSelection(BasicTreeUI.java:3442)
at javax.swing.plaf.basic.BasicTreeUI$Handler.mousePressed(BasicTreeUI.java:3403)
at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:222)
at java.awt.Component.processMouseEvent(Component.java:5485)1at javax.swing.JComponent.processMouseEvent(JComponent.java:3093)
at java.awt.Component.processEvent(Component.java:5253)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3889)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1774)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)