Java做贪吃蛇的一些Bug~

Question

我用eclipse做了一个贪吃蛇的游戏，项目工程表如下：

主要的类GamePanel的代码如下：

package pack;

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

public class GamePanel extends JPanel 
                            implements ActionListener {
    
    
    static final int SCREEN_WIDTH=600
            ,SCREEN_HEIGHT=600;
    static final int UNIT_SIZE=25;
    static final int GAME_UNIT = (SCREEN_WIDTH*SCREEN_HEIGHT) / UNIT_SIZE;
    static final int DELAY = 75;
    static final int x[] = new int[GAME_UNIT],
            y[] = new int[GAME_UNIT];
    int body_parts = 6;
    int apple_eatten;
    int appleX,appleY;
    char direction = 'R';
    int bodyParts = 6;
    boolean running = false;
    Timer timer;
    Random rand;
    
    /**
     * 构造
     */
    GamePanel() {
        rand = new Random();
        setPreferredSize(new Dimension(SCREEN_WIDTH,SCREEN_HEIGHT));
        setBackground(Color.black);
        setFocusable(true);
        addKeyListener(new MyKeyAdapter());
        startGame();
    }
    
    /**函数库*/
    
    /**
     * 开始游戏
     */
    public void startGame() {
        addApple();
        running = true;
        timer = new Timer(DELAY,this);
        timer.start();
    }

    /**
     * 绘制组件
     */
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        draw(g);
    }
    
    /**
     * 添加苹果
     */
    public void addApple() {
        appleX = rand.nextInt((int)SCREEN_WIDTH/UNIT_SIZE)*UNIT_SIZE;
        appleY = rand.nextInt((int)SCREEN_HEIGHT/UNIT_SIZE)*UNIT_SIZE;
        
    }
    
    /**
     * 绘制
     */
    public void draw(Graphics g) {
        
        if (running) {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            g.setColor(Color.white);
            for (int i = 0;i < SCREEN_HEIGHT/UNIT_SIZE;i++)
            {
                g.drawLine(i*UNIT_SIZE, 0, i*UNIT_SIZE, SCREEN_HEIGHT);
            }
            for (int i = 0;i < SCREEN_WIDTH/UNIT_SIZE;i++) 
            {
                g.drawLine(0, i*UNIT_SIZE, SCREEN_WIDTH, i*UNIT_SIZE);
            }
            g.setColor(Color.red);
            g.fillOval(appleX, appleY, UNIT_SIZE, UNIT_SIZE);
            
            for (int i = 0;i < body_parts;i++) {
                if (i==0) {
                    g.setColor(Color.green);
                    g.fillRect(x[i], y[i], UNIT_SIZE, UNIT_SIZE);
                } else {
                    g.setColor(new Color(45,180,0));
                    g.fillRect(x[i], y[i], UNIT_SIZE, UNIT_SIZE);
                }
            }
        }else {
            g.setColor(Color.red);
            g.setFont(new Font("Sans Serif",Font.BOLD,50));
            g.drawString("Game Over", 150, 300);
        }
    }
    
    /**
     * 移动
    */
    public void move() {
        for (int i = bodyParts; i > 0 ; i--) {
            x[i] = x[i-1];
            y[i] = y[i-1];
        }
        
        switch(direction) {
        case 'U':
            y[0] = y[0] - UNIT_SIZE;
            break;
        case 'D':
            y[0] = y[0] + UNIT_SIZE;
            break;
        case 'L':
            x[0] = x[0] - UNIT_SIZE;
            break;
        case 'R':
            x[0] = x[0] + UNIT_SIZE;
            break;
        }
    }
    
    /**
     * 侦测碰到苹果
     */
    public void sensingTouchingApple() {
        if ((x[0]==appleX) && (y[0]==appleY)) {
            body_parts++;
            apple_eatten++;
            addApple();
        }
    }
    
    /**
     * 侦测碰撞
     */
    public void sensingCollisions() {
        //侦测自己碰到自己
        for (int i = body_parts;i > 0;i--) {
            if ((x[0]==x[i])&&(y[0]==y[i])) {
                running = false;
            }
        }
        //侦测碰到边缘
        if ((x[0]<0) || (x[0]>SCREEN_WIDTH) || (y[0]>SCREEN_HEIGHT) || (y[0]<0)) {
            running =false;
        }
        
        //不运行了
        if (!running) {
            timer.stop();
        }
    }
    
    /**
     * 接口函数
     */
    @Override
    public void actionPerformed(ActionEvent e) {
        if (running) {
            move();
            sensingTouchingApple();
            sensingCollisions();
        }
        repaint();
    }
    
    /**
     * 钥匙匹配器
     */
    public class MyKeyAdapter extends KeyAdapter{
        @Override
        public void keyPressed(KeyEvent e) {
            switch (e.getKeyCode()) {
            case KeyEvent.VK_LEFT:
                if (direction!='R')
                {
                    direction = 'L';
                }
                break;
            case KeyEvent.VK_RIGHT:
                if (direction!='L')
                {
                    direction = 'R';
                }
                break;
            case KeyEvent.VK_UP:
                if (direction!='D')
                {
                    direction = 'U';
                }
                break;
            case KeyEvent.VK_DOWN:
                if(direction!='U')
                {
                    direction = 'D';
                }
                break;
            }
        }
    }
}

GameFrame代码如下：

package pack;

import javax.swing.*;

public class GameFrame extends JFrame{

    /**
     * 构造
     */
    public GameFrame() {
        
        //属性
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(600,600);
        setLocationRelativeTo(null);
        setResizable(false);
        
        //添加游戏面板
        GamePanel panel = new GamePanel();
        getContentPane().add(panel);
    }

}

start类就是入口了。
这个游戏有一些bug，请大家修复！