用java写一个简单的随机生成井字棋棋子的程序

import java.awt.BorderLayout;import java.awt.Color;import java.awt.GridLayout;import java.util.Random;import javax.swing.Icon;import javax.swing.ImageIcon;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.border.TitledBorder;public class TicTacToe {    public static void main(String[] args) {        String[] imgs = { "imgs//x.png", "imgs//o.png", "" };        Random rnd = new Random();        JFrame mywin = new JFrame("窗口");        mywin.setSize(400, 440);        mywin.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        mywin.setLocationRelativeTo(null);        JPanel pan = new JPanel();        /*         for (int i = 1; i <= 9; i++) {             String img = imgs[rnd.nextInt(3)];             JButton btn = new JButton("");             btn.setBackground(new Color(255,255,255));             btn.setIcon(new ImageIcon(img));             pan.add(btn);         }         */         //用按鈕做出的棋子和棋盘更好看点，代码如上        for (int i = 1; i <= 9; i++) {            String img = imgs[rnd.nextInt(3)];            JLabel pan1 = new JLabel();            pan1.setIcon(new ImageIcon(img));            pan.add(pan1);        }        pan.setLayout(new GridLayout(3, 3));        mywin.add(pan);        mywin.setVisible(true);    }}