关于Label 上图片更换的问题~~~~~

package com.freish;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;

public class LabelTest extends JFrame {
    private Container container;
    private JLabel label;
    private JButton button;
    private ImageIcon[] icon = new ImageIcon[]{new ImageIcon("image/1.jpg"),
            new ImageIcon("image/2.jpg"),new ImageIcon("image/3.jpg"),
            new ImageIcon("image/4.jpg"),new ImageIcon("image/5.jpg"),
            new ImageIcon("image/6.jpg"),new ImageIcon("image/7.jpg")};

    public LabelTest() {
        super("LabelTest");
        label = new JLabel(new ImageIcon("image/1.jpg")); // 创建Label，并在Label上添加第一张图片
        //label.setBounds(27, 22, 200, 150);
        container = getContentPane();
        container.add(label);

        button = new JButton("更改图片");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                Random rnd = new Random();
                int num = rnd.nextInt(icon.length);
                label.setIcon(icon[num]);
            }
        });

        container.add(button,BorderLayout.SOUTH);
        
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        
        Dimension frameSize = getSize();
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        setLocation((screenSize.width - frameSize.width)/2,(screenSize.height - frameSize.height)/2);
        
        setVisible(true);
    }
    public static void main(String[] args) {
        new LabelTest();
    }
}