用java编写井字游戏“Tictactoe.java”,该页面带有简单的菜单栏，且只有一个“操作”菜单，下含“开始游戏”，“保存游戏”，“退出游戏”三个菜单条，游戏界面包括下拉框——九宫格选项（33，44；...10*10),页面可随用户选择变换大小，有“开始”，“再来一局”按钮：要求程序启动后，程序界面为灰色，需要启动菜单栏的开始游戏才能允许九宫格选项，点击开始/再来一局按钮游戏开始对战，双方各执“X”,"O"不同符号表示对战

好的，下面是一个基本的实现示例：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Tictactoe extends JFrame {
    private static final long serialVersionUID = 1L;
    private JPanel gamePanel;
    private JComboBox<String> sizeComboBox;
    private JButton startButton;
    private JButton restartButton;
    private JMenuItem startMenuItem;
    private JMenuItem saveMenuItem;
    private JMenuItem exitMenuItem;
    private JFileChooser fileChooser;

    private char[][] board;
    private char currentPlayer;
    private boolean gameEnded;

    public Tictactoe() {
        // 设置窗口标题和大小
        super("Tictactoe");
        setSize(400, 400);

        // 创建菜单栏和菜单条
        JMenuBar menuBar = new JMenuBar();
        JMenu operationMenu = new JMenu("操作");
        menuBar.add(operationMenu);
        setJMenuBar(menuBar);

        // 创建菜单项并添加到菜单条中
        startMenuItem = new JMenuItem("开始游戏");
        operationMenu.add(startMenuItem);
        saveMenuItem = new JMenuItem("保存游戏");
        operationMenu.add(saveMenuItem);
        exitMenuItem = new JMenuItem("退出游戏");
        operationMenu.add(exitMenuItem);

        // 为菜单项添加事件处理程序
        startMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                startGame();
            }
        });
        saveMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                saveGame();
            }
        });
        exitMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });

        // 创建下拉框并添加到内容面板中
        String[] sizes = {"3x3", "4x4", "5x5", "6x6", "7x7", "8x8", "9x9", "10x10"};
        sizeComboBox = new JComboBox<>(sizes);
        sizeComboBox.setEnabled(false);
        JPanel controlPanel = new JPanel(new FlowLayout());
        controlPanel.add(new JLabel("九宫格大小:"));
        controlPanel.add(sizeComboBox);
        startButton = new JButton("开始");
        startButton.setEnabled(false);
        startButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                startButton.setEnabled(false);
                sizeComboBox.setEnabled(false);
                gamePanel.removeAll();
                gamePanel.setLayout(new GridLayout(getBoardSize(), getBoardSize()));
                board = new char[getBoardSize()][getBoardSize()];
                currentPlayer = 'X';
                gameEnded = false;
                for (int i = 0; i < getBoardSize(); i++) {
                    for (int j = 0; j < getBoardSize(); j++) {
                        JButton button = new JButton();
                        button.addActionListener(new ActionListener() {
                            public void actionPerformed(ActionEvent e) {
                                if (!gameEnded) {
                                    JButton clickedButton = (JButton) e.getSource();
                                    int row = getButtonRow(clickedButton);
                                    int col = getButtonCol(clickedButton);
                                    if (board[row][col] == '\0') {
                                        board[row][col] = currentPlayer;
                                        clickedButton.setText("" + currentPlayer);
                                        if (checkWin(row, col)) {
                                            JOptionPane.showMessageDialog(Tictactoe.this, "恭喜" + currentPlayer + "获胜！");
                                            gameEnded = true;
                                            startButton.setEnabled(true);
                                        } else if (checkTie()) {
                                            JOptionPane.showMessageDialog(Tictactoe.this, "平局！");
                                            gameEnded = true;
                                            startButton.setEnabled(true);
                                        } else {
                                            currentPlayer = (currentPlayer == 'X') ? 'O' : 'X';
                                        }
                                    }
                                }
                            }
                        });
                        gamePanel.add(button);
                    }
                }
                gamePanel.revalidate();
                gamePanel.repaint();
            }
        });
        controlPanel.add(startButton);
        restartButton = new JButton("再来一局");
        restartButton.setEnabled(false);
        restartButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                for (int i = 0; i < getBoardSize(); i++) {
                    for (int j = 0; j < getBoardSize(); j++) {
                        board[i][j] = '\0';
                    }
                }
                for (Component c : gamePanel.getComponents()) {
                    JButton button = (JButton) c;
                    button.setText("");
                }
                currentPlayer = 'X';
                gameEnded = false;
                restartButton.setEnabled(false);
            }
        });
        controlPanel.add(restartButton);
        add(controlPanel, BorderLayout.NORTH);

        // 创建游戏面板并添加到内容面板中
        gamePanel = new JPanel();
        gamePanel.setBackground(Color.GRAY);
        add(gamePanel, BorderLayout.CENTER);

        // 创建文件选择器
        fileChooser = new JFileChooser();
    }

    private int getBoardSize() {
        String size = (String) sizeComboBox.getSelectedItem();
        return Integer.parseInt(size.substring(0, size.indexOf('x')));
    }

    private int getButtonRow(JButton button) {
        return gamePanel.getComponentZOrder(button) / getBoardSize();
    }

    private int getButtonCol(JButton button) {
        return gamePanel.getComponentZOrder(button) % getBoardSize();
    }

    private boolean checkWin(int row, int col) {
        // 检查行
        for (int i = 0; i < getBoardSize(); i++) {
            if (board[row][i] != currentPlayer) {
                break;
            }
            if (i == getBoardSize() - 1) {
                return true;
            }
        }
        // 检查列
        for (int i = 0; i < getBoardSize(); i++) {
            if (board[i][col] != currentPlayer) {
                break;
            }
            if (i == getBoardSize() - 1) {
                return true;
            }
        }
        // 检查对角线
        if (row == col) {
            for (int i = 0; i < getBoardSize(); i++) {
                if (board[i][i] != currentPlayer) {
                    break;
                }
                if (i == getBoardSize() - 1) {
                    return true;
                }
            }
        }
        if (row + col == getBoardSize() - 1) {
            for (int i = 0; i < getBoardSize(); i++) {
                if (board[i][getBoardSize() - i - 1] != currentPlayer) {
                    break;
                }
                if (i == getBoardSize() - 1) {
                    return true;
                }
            }
        }
        return false;
    }

    private boolean checkTie() {
        for (int i = 0; i < getBoardSize(); i++) {
            for (int j = 0; j < getBoardSize(); j++) {
                if (board[i][j] == '\0') {
                    return false;
                }
            }
        }
        return true;
    }

    private void startGame() {
        sizeComboBox.setEnabled(true);
    }

    private void saveGame() {
        int result = fileChooser.showSaveDialog(this);
        if (result == JFileChooser.APPROVE_OPTION) {
            // TODO: 保存游戏状态到文件
        }
    }

    public static void main(String[] args) {
        Tictactoe game = new Tictactoe();
        game.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        game.setVisible(true);
    }
}

在这个示例中，我们创建了一个Tictactoe类作为游戏的主类，继承自JFrame类。在构造函数中，我们创建了菜单栏、下拉框、按钮和游戏面板，并且为菜单项和按钮添加了事件处理程序。我们使用二维数组来表示游戏面板，并且使用GridLayout布局管理器来动态改变游戏面板的大小。当用户点击一个按钮时，我们检查游戏是否结束，如果没有结束，我们更新游戏状态并检查是否有获胜者或平局。最后，我们使用文件选择器来实现保存游戏状态的功能。

请注意，这只是一个基本的实现示例，您可能需要根据您的具体需求进行修改和扩展。