public class GreedSnake implements KeyListener{
  JFrame mainFrame;
  Canvas paintCanvas;
  JLabel labelScore;
  SnakeModel snakeModel = null;

  public static final int canvasWidth = 200;
  public static final int canvasHeight = 300;

  public static final int nodeWidth = 10;
  public static final int nodeHeight = 10;

  public GreedSnake() {
    mainFrame = new JFrame("GreedSnake");

    Container cp = mainFrame.getContentPane();
 
    labelScore = new JLabel("Score:");
    cp.add(labelScore, BorderLayout.NORTH);

    paintCanvas = new Canvas();
    paintCanvas.setSize(canvasWidth+1,canvasHeight+1);
    paintCanvas.addKeyListener(this);
    cp.add(paintCanvas, BorderLayout.CENTER);

    JPanel panelButtom = new JPanel();
    panelButtom.setLayout(new BorderLayout());
    JLabel labelHelp;
    labelHelp = new JLabel("PageUp, PageDown for speed;", JLabel.CENTER);
    panelButtom.add(labelHelp, BorderLayout.NORTH);

    labelHelp = new JLabel("ENTER or R or S for start;", JLabel.CENTER);
    panelButtom.add(labelHelp, BorderLayout.CENTER);
    labelHelp = new JLabel("SPACE or P for pause",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();
  }

  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();
          break;
        case KeyEvent.VK_SUBTRACT:
        case KeyEvent.VK_PAGE_DOWN:
          snakeModel.speedDown();
          break;
        case KeyEvent.VK_SPACE:
        case KeyEvent.VK_P:
          snakeModel.changePauseState();
          break;
        default:
      }

    if (keyCode == KeyEvent.VK_R ||
        keyCode == KeyEvent.VK_S ||
        keyCode == KeyEvent.VK_ENTER){
      snakeModel.running = false;

      begin();
    }
  }

  public void keyReleased(KeyEvent e){
  }

  public void keyTyped(KeyEvent e){
  }
  void repaint(){
    Graphics g = paintCanvas.getGraphics();

    //draw background
    g.setColor(Color.WHITE);
    g.fillRect(0,0,canvasWidth,canvasHeight);

    // 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();
  }

  private void drawNode(Graphics g, Node n){
    g.fillRect(n.x*nodeWidth,
               n.y*nodeHeight,
               nodeWidth-1,
               nodeHeight-1);
  }
 
  public void updateScore(){
    String s = "Score: " + snakeModel.score;
    labelScore.setText(s);
  }

  void begin(){
    if (snakeModel == null || !snakeModel.running){
      snakeModel = new SnakeModel(this,
                                  canvasWidth/nodeWidth,
                                  canvasHeight/nodeHeight);

      (new Thread(snakeModel)).start();
    }
  }

  public static void main(String[] args){
    GreedSnake gs = new GreedSnake();
  }
}

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

class SnakeModel implements Runnable{
  GreedSnake gs;
  boolean[][] matrix;
  LinkedList nodeArray = new LinkedList();
  Node food;
  int maxX;
  int maxY;
  int direction = 2;
  boolean running = false;

  int timeInterval = 200;
  double speedChangeRate = 0.75;
  boolean paused = false;
 
  int score = 0;
  int countMove = 0;

  // UP and DOWN should be even
  // RIGHT and LEFT should be odd
  public static final int UP = 2;
  public static final int DOWN = 4;
  public static final int LEFT = 1;
  public static final int RIGHT = 3;

  public SnakeModel(GreedSnake gs, int maxX, int maxY){
    this.gs = gs;
    this.maxX = maxX;
    this.maxY = maxY;

    // initial matirx
    matrix = new boolean[maxX][];
    for(int i=0; i<maxX; ++i){
      matrix[i] = new boolean[maxY];

      Arrays.fill(matrix[i],false);
    }

    // initial the snake
    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;
    }

    food = createFood();
    matrix[food.x][food.y] = true;
  }

  public void changeDirection(int newDirection){
    if (direction % 2 != newDirection % 2){
      direction = newDirection;
    }
  }

  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]){
        if(x == food.x && y == food.y){
          nodeArray.addFirst(food);
         
          int scoreGet = (10000 - 200 * countMove) / timeInterval;
          score += scoreGet > 0? scoreGet : 10;
          countMove = 0;

  public void run(){
    running = true;
    while (running){
      try{
        Thread.sleep(timeInterval);
      }
      catch(Exception e){
        break;
      }

      if(!paused){
        if (moveOn()){
          gs.repaint();
        }
        else{
          JOptionPane.showMessageDialog(
              null,
              "you failed",
              "Game Over",
              JOptionPane.INFORMATION_MESSAGE);
          break;
        }
      }
    }
    running = false;
  }

  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);
  }

  public void speedUp(){
    timeInterval *= speedChangeRate;
  }

  public void speedDown(){
    timeInterval /= speedChangeRate;
  }

  public void changePauseState(){
    paused = !paused;
  }

  public String toString(){
    String result = "";
    for(int i=0; i<nodeArray.size(); ++i){
      Node n = (Node)nodeArray.get(i);
      result += "[" + n.x + "," + n.y + "]";
    }
    return result;
  }
}

class Node{
  int x;
  int y;
  Node(int x, int y){
    this.x = x;
    this.y = y;
  }
}