Java 贪吃蛇游戏：添加不可回头和撞身体结束功能

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

public class test extends JFrame implements ActionListener { String name; JButton jbn = new JButton('开始'); D jpn = new D();

test() {
    Container cn = getContentPane();
    cn.setLayout(new BorderLayout());
    cn.add(jbn, BorderLayout.NORTH);
    cn.add(jpn, BorderLayout.CENTER);
    jbn.addActionListener(this);
    setSize(600, 400);
    setVisible(true);
}

public void actionPerformed(ActionEvent e) {
    Thread t1 = new Thread(jpn);
    t1.start();
    jpn.requestFocus(true);
}

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

}

class D extends JPanel implements Runnable, KeyListener { int x = 10; int direction = 0; Random r = new Random(); Vector v = new Vector(); Point food = new Point();

D() {
    v.add(new Point(20, 10));
    v.add(new Point(20, 10));
    v.add(new Point(20, 10));
    v.add(new Point(20, 10));

    int t = r.nextInt(20);
    food.x = t * 10;
    food.y = t * 10;
    addKeyListener(this);
}



public void run() {
    try {
        while (true) {
            for (int i = 0; i < v.size() - 1; i++) {
                Point p = v.get(i);
                Point p2 = v.get(i + 1);
                p.x = p2.x;
                p.y = p2.y;
            }
            if (direction == 0) {
                Point p = v.get(v.size() - 1);
                p.x = p.x + 10;
                // 撞墙检测以及得分系统
                if (p.x > 580) {
                    JOptionPane.showMessageDialog(null, '你GG了! 最终得分为 ' + (v.size() - 4));
                    System.exit(0);
                }
            }
            if (direction == 1) {
                Point p = v.get(v.size() - 1);
                p.x = p.x - 10;
                // 撞墙检测以及得分系统
                if (p.x < 10) {
                    JOptionPane.showMessageDialog(null, '你GG了! 最终得分为 ' + (v.size() - 4));
                    System.exit(0);
                }
            }
            if (direction == 2) {
                Point p = v.get(v.size() - 1);
                p.y = p.y - 10;
                // 撞墙检测以及得分系统
                if (p.y < 10) {
                    JOptionPane.showMessageDialog(null, '你GG了! 最终得分为 ' + (v.size() - 4));
                    System.exit(0);
                }
            }
            if (direction == 3) {
                Point p = v.get(v.size() - 1);
                p.y = p.y + 10;
                // 撞墙检测以及得分系统
                if (p.y > 370) {
                    JOptionPane.showMessageDialog(null, '你GG了! 最终得分为 ' + (v.size() - 4));
                    System.exit(0);
                }
            }

            // 撞到身体检测以及得分系统
            for (int i = 0; i < v.size() - 1; i++) {
                Point p = v.get(i);
                Point p2 = v.get(v.size() - 1);
                if (p.x == p2.x && p.y == p2.y) {
                    JOptionPane.showMessageDialog(null, '你GG了! 最终得分为 ' + (v.size() - 4));
                    System.exit(0);
                }
            }

            for (int i = 0; i < v.size(); i++) {
                Point p = v.get(i);
                if (p.x == food.x && p.y == food.y) {
                    int t = r.nextInt(20);
                    food.x = t * 10;
                    food.y = t * 10;

                    v.add(new Point(p.x, p.y));
                    break;
                }
            }
            repaint();
            Thread.sleep(100);
        }
    } catch (Exception e) {

    }
}

public void paint(Graphics g) {
    super.paint(g);
    for (int i = 0; i < v.size(); i++) {
        Point p = v.get(i);
        int x = p.x;
        int y = p.y;
        if (i == v.size() - 1) {
            g.setColor(Color.blue);
            g.fillOval(x, y, 9, 9);
        } else {
            g.setColor(Color.black);
            g.fillOval(x, y, 9, 9);
        }
    }

    int x = food.x;
    int y = food.y;
    g.setColor(Color.red);
    g.fillRect(x, y, 9, 9);
}

public void keyPressed(KeyEvent e) {
    // 不可回头功能
    if (e.getKeyCode() == KeyEvent.VK_UP && direction != 3) {
        direction = 2;
    }
    if (e.getKeyCode() == KeyEvent.VK_DOWN && direction != 2) {
        direction = 3;
    }
    if (e.getKeyCode() == KeyEvent.VK_LEFT && direction != 0) {
        direction = 1;
    }
    if (e.getKeyCode() == KeyEvent.VK_RIGHT && direction != 1) {
        direction = 0;
    }
}

public void keyReleased(KeyEvent e) {

}

public void keyTyped(KeyEvent e) {

}

}