请用Java编写一段贪吃蛇程序

以下是一个简单的Java贪吃蛇程序的代码示例：

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

public class SnakeGame extends JFrame implements KeyListener, ActionListener {
   private int width = 600; // 窗口宽度
   private int height = 600; // 窗口高度
   private int blockSize = 10; // 方块大小
   private int blockNum = width / blockSize * height / blockSize; // 方块数量
   private int[] snakeX = new int[blockNum]; // 蛇身x坐标
   private int[] snakeY = new int[blockNum]; // 蛇身y坐标
   private int snakeLength = 3; // 蛇身长度
   private int foodX; // 食物x坐标
   private int foodY; // 食物y坐标
   private int direction = 0; // 蛇头方向（0：向上，1：向下，2：向左，3：向右）
   private Timer timer; // 定时器

   public SnakeGame() {
      setTitle("贪吃蛇");
      setSize(width, height);
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setVisible(true);
      setResizable(false);
      addKeyListener(this);

      // 初始化蛇身位置
      snakeX[0] = width / blockSize / 2 * blockSize;
      snakeY[0] = height / blockSize / 2 * blockSize;

      // 初始化食物位置
      newFood();

      // 启动定时器
      timer = new Timer(100, this);
      timer.start();
   }

   public void paint(Graphics g) {
      super.paint(g);
      // 绘制蛇身
      g.setColor(Color.GREEN);
      for (int i = 0; i < snakeLength; i++) {
         g.fillRect(snakeX[i], snakeY[i], blockSize, blockSize);
      }
      // 绘制食物
      g.setColor(Color.RED);
      g.fillRect(foodX, foodY, blockSize, blockSize);
   }

   public void keyPressed(KeyEvent e) {
      int key = e.getKeyCode();
      // 改变蛇头方向
      if (key == KeyEvent.VK_UP && direction != 1) {
         direction = 0;
      }
      if (key == KeyEvent.VK_DOWN && direction != 0) {
         direction = 1;
      }
      if (key == KeyEvent.VK_LEFT && direction != 3) {
         direction = 2;
      }
      if (key == KeyEvent.VK_RIGHT && direction != 2) {
         direction = 3;
      }
   }

   public void actionPerformed(ActionEvent e) {
      // 移动蛇身
      for (int i = snakeLength - 1; i > 0; i--) {
         snakeX[i] = snakeX[i - 1];
         snakeY[i] = snakeY[i - 1];
      }
      // 移动蛇头
      if (direction == 0) {
         snakeY[0] -= blockSize;
      }
      if (direction == 1) {
         snakeY[0] += blockSize;
      }
      if (direction == 2) {
         snakeX[0] -= blockSize;
      }
      if (direction == 3) {
         snakeX[0] += blockSize;
      }
      // 判断是否吃到食物
      if (snakeX[0] == foodX && snakeY[0] == foodY) {
         snakeLength++;
         newFood();
      }
      // 判断是否撞墙或自身
      for (int i = 1; i < snakeLength; i++) {
         if (snakeX[i] == snakeX[0] && snakeY[i] == snakeY[0]) {
            gameOver();
         }
      }
      if (snakeX[0] < 0 || snakeX[0] >= width || snakeY[0] < 0 || snakeY[0] >= height) {
         gameOver();
      }
      // 重绘窗口
      repaint();
   }

   private void newFood() {
      foodX = (int) (Math.random() * (width / blockSize)) * blockSize;
      foodY = (int) (Math.random() * (height / blockSize)) * blockSize;
   }

   private void gameOver() {
      timer.stop();
      JOptionPane.showMessageDialog(this, "游戏结束");
      System.exit(0);
   }

   public static void main(String[] args) {
      new SnakeGame();
   }

   public void keyTyped(KeyEvent e) {}
   public void keyReleased(KeyEvent e) {}
}

这个程序使用Java的Swing框架实现了一个简单的贪吃蛇游戏。游戏窗口大小为600x600，每个方块大小为10x10，蛇身和食物都是方块。通过键盘上下左右箭头控制蛇头方向，蛇身长度随着吃到食物逐渐增加，当蛇头碰到墙或者自身时游戏结束。程序使用了定时器来不断更新蛇身和食物位置，并通过重绘窗口来实现动态效果。