java 贪食蛇代码

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

//Main Class

public class GreedSnake extends KeyAdapter{

 JFrame mainFrame;
 Canvas paintCanvas;
 JLabel labelScore;//计分牌
 SnakeModel snakeModel=null;// 蛇
 public static final int DEFAULT_WIDTH=500;
 public static final int DEFAULT_HEIGHT=300;
 public static final int nodeWidth=10;
 public static final int nodeHeight=10;

 //GreedSnake():初始化游戏界面

 public GreedSnake(){
 
  //设置界面元素
  mainFrame=new JFrame("贪吃蛇游戏");
  Container cp=mainFrame.getContentPane();
  labelScore=new JLabel("所得分数为:",JLabel.CENTER);
  cp.add(labelScore,BorderLayout.NORTH);
  paintCanvas=new Canvas();
  paintCanvas.setSize(DEFAULT_WIDTH+1,DEFAULT_HEIGHT+1);
  paintCanvas.addKeyListener(this);

  cp.add(paintCanvas,BorderLayout.CENTER);
  JPanel panelButtom=new JPanel();
  panelButtom.setLayout(new BorderLayout());
  JLabel labelHelp;// 帮助信息
  labelHelp=new JLabel("按 PageUP 或 PageDown 键改变速度",JLabel.CENTER);
  panelButtom.add(labelHelp,BorderLayout.NORTH);
  labelHelp=new JLabel("按 Enter 或 S 键重新开始游戏",JLabel.CENTER);
  panelButtom.add(labelHelp,BorderLayout.CENTER);
  labelHelp=new JLabel("按 SPACE 键或 P 键暂停游戏",JLabel.CENTER);
  panelButtom.add(labelHelp,BorderLayout.SOUTH);
  cp.add(panelButtom,BorderLayout.SOUTH);
  mainFrame.addKeyListener(this);
  mainFrame.pack();
  mainFrame.setResizable(false);
  mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  mainFrame.setVisible(true);
  begin();
 }
 
 //keyPressed():按键检测
 
 public void keyPressed(KeyEvent e){
 
  int keyCode=e.getKeyCode();
  if(snakeModel.running) 
   switch(keyCode){  
    case KeyEvent.VK_UP:
     snakeModel.changeDirection(SnakeModel.UP);
     break;
    case KeyEvent.VK_DOWN: