JAVA swing JTree updateUI() 和 repaint()

[code="java"]
package com.hello.model;

import java.util.concurrent.TimeUnit;

import javax.swing.*;
import javax.swing.tree.*;

public class NewTree {

JFrame frame = new JFrame();
DefaultMutableTreeNode parent = new DefaultMutableTreeNode("baidu");
DefaultMutableTreeNode child1 = new DefaultMutableTreeNode("sohu");
DefaultMutableTreeNode child11 = new DefaultMutableTreeNode("sina");
DefaultMutableTreeNode child12 = new DefaultMutableTreeNode("taobao");
DefaultMutableTreeNode child2 = new DefaultMutableTreeNode("163");

JTree tree = new JTree(parent);

private void init() throws InterruptedException {

    parent.add(child1);
    parent.add(child2);

    child1.add(child11);
    child1.add(child12);

    tree.expandPath(new TreePath(child1.getPath()));

    frame.add(new JScrollPane(tree));
    frame.pack();
    frame.setVisible(true);

    TimeUnit.SECONDS.sleep(5);
    child1.remove(child11);
        //tree.updateUI(); //1处代码可以更新UI
    tree.repaint();   //2处代码无法更新UI
}

public static void main(String[] args) throws InterruptedException {
    new NewTree().init();
}

}

[/code]

为什么1处代码可以更新UI，能够看到节点删除的效果，而2处就不可以？

updateUI()通常当look and feel发生变化时调用，从UIManager中获取新的L&F，应用到组件上，重绘的范围比较大，要稍微慢一些。repaint()只是通知RepaintManager重绘组件，不包括UI和布局的管理。