Java写的小游戏贪吃蛇代码

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);// 设置窗口大小不能变化    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:      snakeModel.changeDirection(SnakeModel.DOWN);      break;     case KeyEvent.VK_LEFT:      snakeModel.changeDirection(SnakeModel.LEFT);      break;     case KeyEvent.VK_RIGHT:      snakeModel.changeDirection(SnakeModel.RIGHT);      break;     case KeyEvent.VK_ADD:     case KeyEvent.VK_PAGE_UP:      snakeModel.speedUp();// 加速      break;     case KeyEvent.VK_SUBTRACT:     case KeyEvent.VK_PAGE_DOWN:      snakeModel.speedDown();// 减速      break;     case KeyEvent.VK_SPACE:     case KeyEvent.VK_P:      snakeModel.changePauseState();// 暂停或继续      break;     default:     }    // 重新开始    if (keyCode == KeyEvent.VK_S || keyCode == KeyEvent.VK_ENTER) {     snakeModel.running = false;     begin();    }   }     // repaint（）：绘制游戏界面（包括蛇和食物）     void repaint() {    Graphics g = paintCanvas.getGraphics();    // draw background    g.setColor(Color.LIGHT_GRAY);    g.fillRect(0, 0, DEFAULT_WIDTH, DEFAULT_HEIGHT);    // draw the snake    g.setColor(Color.BLACK);    LinkedList na = snakeModel.nodeArray;    Iterator it = na.iterator();    while (it.hasNext()) {       Node n = (Node) it.next();     drawNode(g, n);    }    // draw the food    g.setColor(Color.RED);    Node n = snakeModel.food;    drawNode(g, n);    updateScore();   }     // drawNode（）：绘画某一结点（蛇身或食物）     private void drawNode(Graphics g, Node n) {    g.fillRect(n.x * nodeWidth, n.y * nodeHeight, nodeWidth - 1, nodeHeight - 1);   }     // updateScore（）：改变计分牌     public void updateScore() {    String s = "所得分数为: " + snakeModel.score;    labelScore.setText(s);   }     // begin（）：游戏开始，放置贪吃蛇     void begin() {      if (snakeModel == null || !snakeModel.running) {     snakeModel = new SnakeModel(this, DEFAULT_WIDTH / nodeWidth, DEFAULT_HEIGHT / nodeHeight);     (new Thread(snakeModel)).start();    }   }     // main（）：主函数     public static void main(String[] args) {      GreedSnake gs = new GreedSnake();   }  }    // Node:结点类    class Node {   int x;     int y;     Node(int x, int y) {    this.x = x;    this.y = y;   }  }    // SnakeModel:贪吃蛇模型    class SnakeModel implements Runnable {     GreedSnake gs;     boolean[][] matrix;// 界面数据保存在数组里     LinkedList nodeArray = new LinkedList();     Node food;     int maxX;// 最大宽度     int maxY;// 最大长度     int direction = 2;// 方向     boolean running = false;     int timeInterval = 200;// 间隔时间（速度）     double speedChangeRate = 0.75;// 速度改变程度     boolean paused = false;// 游戏状态     int score = 0;     int countMove = 0;     // UP和DOWN是偶数，RIGHT和LEFT是奇数   public static final int UP = 2;     public static final int DOWN = 4;     public static final int LEFT = 1;     public static final int RIGHT = 3;     // GreedModel():初始化界面     public SnakeModel(GreedSnake gs, int maxX, int maxY) {      this.gs = gs;    this.maxX = maxX;    this.maxY = maxY;    matrix = new boolean[maxX][];    for (int i = 0; i < maxX; ++i) {     matrix[i] = new boolean[maxY];     Arrays.fill(matrix[i], false);// 没有蛇和食物的地区置false    }    // 初始化贪吃蛇    int initArrayLength = maxX > 20 ? 10 : maxX / 2;    for (int i = 0; i < initArrayLength; ++i) {     int x = maxX / 2 + i;     int y = maxY / 2;     nodeArray.addLast(new Node(x, y));     matrix[x][y] = true;// 蛇身处置true    }    food = createFood();    matrix[food.x][food.y] = true;// 食物处置true   }     // changeDirection():改变运动方向     public void changeDirection(int newDirection) {      if (direction % 2 != newDirection % 2) {// 避免冲突     direction = newDirection;    }   }     // moveOn():贪吃蛇运动函数     public boolean moveOn() {      Node n = (Node) nodeArray.getFirst();    int x = n.x;    int y = n.y;    switch (direction) {    case UP:     y--;     break;    case DOWN:     y++;     break;    case LEFT:     x--;     break;    case RIGHT:     x++;     break;    }    if ((0 <= x && x < maxX) && (0 <= y && y < maxY)) {       if (matrix[x][y]) {// 吃到食物或者撞到身体        if (x == food.x && y == food.y) {// 吃到食物         nodeArray.addFirst(food);// 在头部加上一结点       // 计分规则与移动长度和速度有关       int scoreGet = (10000 - 200 * countMove) / timeInterval;       score += scoreGet > 0 ? scoreGet : 10;       countMove = 0;       food = createFood();       matrix[food.x][food.y] = true;       return true;      } else       return false;// 撞到身体     } else {// 什么都没有碰到      nodeArray.addFirst(new Node(x, y));// 加上头部      matrix[x][y] = true;      n = (Node) nodeArray.removeLast();// 去掉尾部      matrix[n.x][n.y] = false;      countMove++;      return true;     }    }    return false;// 越界（撞到墙壁）   }     /* 发了一份贪吃蛇游戏的代码，谁能帮我解释一下，贪吃蛇程序的运行过程，运行步骤 */   // run():贪吃蛇运动线程     public void run() {    running = true;    while (running) {     try {      Thread.sleep(timeInterval);     } catch (Exception e) {      break;     }     if (!paused) {        if (moveOn()) {// 未结束       gs.repaint();      } else {// 游戏结束       JOptionPane.showMessageDialog(null, "GAME OVER", "Game Over", JOptionPane.INFORMATION_MESSAGE);       break;      }     }    }    running = false;   }     // createFood():生成食物及放置地点     private Node createFood() {      int x = 0;    int y = 0;    do {     Random r = new Random();     x = r.nextInt(maxX);     y = r.nextInt(maxY);    } while (matrix[x][y]);    return new Node(x, y);   }     // speedUp():加快蛇运动速度     public void speedUp() {    timeInterval *= speedChangeRate;   }     // speedDown():放慢蛇运动速度     public void speedDown() {      timeInterval /= speedChangeRate;   }     // changePauseState(): 改变游戏状态（暂停或继续）     public void changePauseState() {      paused = !paused;   }  }