用Java写一个贪吃蛇小游戏并注释

非常感谢您的提问，我可以为您提供一个简单的Java贪吃蛇小游戏的代码，并附上注释，代码如下：

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

public class SnakeGame extends JFrame implements ActionListener {
    private static final long serialVersionUID = 1L;
    private final int WIDTH = 300; // 游戏窗口的宽度
    private final int HEIGHT = 300; // 游戏窗口的高度
    private final int DOT_SIZE = 10; // 蛇身的大小
    private final int ALL_DOTS = 900; // 游戏区域最多能容纳的蛇身数量
    private final int RAND_POS = 29; // 食物出现的位置范围
    private final int DELAY = 140; // 游戏速度，单位为毫秒

    private int x[] = new int[ALL_DOTS]; // 蛇身的横坐标
    private int y[] = new int[ALL_DOTS]; // 蛇身的纵坐标
    private int dots; // 蛇身的数量
    private int apple_x; // 食物的横坐标
    private int apple_y; // 食物的纵坐标

    private Timer timer; // 游戏计时器
    private boolean leftDirection = false; // 蛇是否向左移动
    private boolean rightDirection = true; // 蛇是否向右移动
    private boolean upDirection = false; // 蛇是否向上移动
    private boolean downDirection = false; // 蛇是否向下移动
    private boolean inGame = true; // 游戏是否结束

    public SnakeGame() {
        initGame();
    }

    private void initGame() {
        // 初始化蛇身
        dots = 3;
        for (int i = 0; i < dots; i++) {
            x[i] = 50 - i * DOT_SIZE;
            y[i] = 50;
        }

        // 初始化食物
        locateApple();

        // 初始化游戏窗口
        setTitle("贪吃蛇小游戏");
        setSize(WIDTH, HEIGHT);
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        // 添加键盘监听器
        addKeyListener(new TAdapter());

        // 初始化游戏计时器
        timer = new Timer(DELAY, this);
        timer.start();
    }

    private void locateApple() {
        // 随机生成食物的位置
        int r = (int) (Math.random() * RAND_POS);
        apple_x = r * DOT_SIZE;
        r = (int) (Math.random() * RAND_POS);
        apple_y = r * DOT_SIZE;
    }

    private void checkApple() {
        // 检查蛇是否吃到了食物
        if ((x[0] == apple_x) && (y[0] == apple_y)) {
            dots++;
            locateApple();
        }
    }

    private void checkCollision() {
        // 检查蛇是否碰到了游戏区域的边缘或自己的身体
        for (int i = dots; i > 0; i--) {
            if ((i > 4) && (x[0] == x[i]) && (y[0] == y[i])) {
                inGame = false;
            }
        }
        if (y[0] >= HEIGHT) {
            inGame = false;
        }
        if (y[0] < 0) {
            inGame = false;
        }
        if (x[0] >= WIDTH) {
            inGame = false;
        }
        if (x[0] < 0) {
            inGame = false;
        }
        if (!inGame) {
            timer.stop();
        }
    }

    private void move() {
        // 移动蛇身
        for (int i = dots; i > 0; i--) {
            x[i] = x[(i - 1)];
            y[i] = y[(i - 1)];
        }
        if (leftDirection) {
            x[0] -= DOT_SIZE;
        }
        if (rightDirection) {
            x[0] += DOT_SIZE;
        }
        if (upDirection) {
            y[0] -= DOT_SIZE;
        }
        if (downDirection) {
            y[0] += DOT_SIZE;
        }
    }

    private void doDrawing(Graphics g) {
        // 绘制游戏区域
        if (inGame) {
            g.setColor(Color.red);
            g.fillOval(apple_x, apple_y, DOT_SIZE, DOT_SIZE);
            for (int i = 0; i < dots; i++) {
                if (i == 0) {
                    g.setColor(Color.green);
                    g.fillRect(x[i], y[i], DOT_SIZE, DOT_SIZE);
                } else {
                    g.setColor(Color.blue);
                    g.fillRect(x[i], y[i], DOT_SIZE, DOT_SIZE);
                }
            }
            Toolkit.getDefaultToolkit().sync();
        } else {
            gameOver(g);
        }
    }

    private void gameOver(Graphics g) {
        // 游戏结束
        String msg = "Game Over";
        Font small = new Font("Helvetica", Font.BOLD, 14);
        FontMetrics metr = getFontMetrics(small);

        g.setColor(Color.black);
        g.setFont(small);
        g.drawString(msg, (WIDTH - metr.stringWidth(msg)) / 2, HEIGHT / 2);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // 游戏计时器触发事件
        if (inGame) {
            checkApple();
            checkCollision();
            move();
        }
        repaint();
    }

    private class TAdapter extends KeyAdapter {
        // 键盘监听器
        @Override
        public void keyPressed(KeyEvent e) {
            int key = e.getKeyCode();
            if ((key == KeyEvent.VK_LEFT) && (!rightDirection)) {
                leftDirection = true;
                upDirection = false;
                downDirection = false;
            }
            if ((key == KeyEvent.VK_RIGHT) && (!leftDirection)) {
                rightDirection = true;
                upDirection = false;
                downDirection = false;
            }
            if ((key == KeyEvent.VK_UP) && (!downDirection)) {
                upDirection = true;
                leftDirection = false;
                rightDirection = false;
            }
            if ((key == KeyEvent.VK_DOWN) && (!upDirection)) {
                downDirection = true;
                leftDirection = false;
                rightDirection = false;
            }
        }
    }

    public static void main(String[] args) {
        // 启动游戏
        EventQueue.invokeLater(() -> {
            SnakeGame ex = new SnakeGame();
            ex.setVisible(true);
        });
    }
}

希望这个代码能够帮助到您，如果您有任何问题或需要进一步的帮助，请随时联系我。