[Java] Problem bei Snake

import java.awt.*;
import java.awt.image.*;
import java.util.concurrent.locks.*;


public class Ausfuehren 
{
 
 static ReentrantLock lock = new ReentrantLock();
 static Spiel spiel = new Spiel();
 static VolatileImage display;
 static Image hinterg;
 static Image kopf;
 static Image koerper;
 static Image futter;
 static int score = 0;
 
 public static void main(String[] args) 
 {
 
 hinterg = Toolkit.getDefaultToolkit().getImage("bg.png");
 kopf = Toolkit.getDefaultToolkit().getImage("kopf.png");
 koerper = Toolkit.getDefaultToolkit().getImage("koerper.png");
 futter = Toolkit.getDefaultToolkit().getImage("futter.png");
 
 HFenster f = new HFenster();
 f.setVisible(true);
 f.setEnabled(true);
 f.setSize(800, 600);
 
 display = f.getGraphicsConfiguration().createCompatibleVolatileImage(f.getWidth(), f.getHeight());
 
 while (true) 
 {
 
 spiel.play();
 lock.lock();
 
 Graphics g = display.getGraphics();
 
 g.clearRect(0,0, f.getWidth(), f.getHeight());
 g.drawImage(hinterg, 0, 0, null);
 g.drawImage(kopf, spiel.snake.stellen.get(0).posx * 10,600 - spiel.snake.stellen.get(0).posy * 10, null);
 
 for(int i = 1; i<spiel.snake.stellen.size(); i++) 
 {
 g.drawImage(koerper, spiel.snake.stellen.get(i).posx * 10,600 - spiel.snake.stellen.get(i).posy * 10, null);
 }
 
 g.drawImage(futter, spiel.futterx * 10, 600 - spiel.futtery * 10, null);
 

 
 f.repaint(); 
 lock.unlock();
 
 try 
 {
 Thread.currentThread().sleep(50);
 }
 catch (InterruptedException e) {
 System.exit(14);
 }
 }
 
 }

}

import java.util.*;

public class Snake 
{

 ArrayList<Koerper> stellen = new ArrayList<Koerper>();
 
 public final static int UP = 0;
 public final static int DOWN = 1;
 public final static int LEFT = 2;
 public final static int RIGHT = 3;
 public int direction;
 
 public class Koerper 
 {
 int posx;
 int posy;
 
 public Koerper(int x, int y) 
 {
 posx = x;
 posy = y;
 }
 }
 
 public void move() 
 {

 for (int i=stellen.size()-1; i>0; i--) 
 {
 stellen.get(i).posx = stellen.get(i-1).posx;
 stellen.get(i).posy = stellen.get(i-1).posy;
 }
 
 if (direction == UP) 
 {
 stellen.get(0).posy += 1;
 }
 
 if (direction == DOWN) 
 {
 stellen.get(0).posy -= 1;
 }
 
 if (direction == LEFT) 
 {
 stellen.get(0).posx -= 1;
 }
 
 if (direction == RIGHT) 
 {
 stellen.get(0).posx += 1;
 }
 }
 
 public Snake() 
 {
 
 direction = UP;
 Koerper head = new Koerper(40, 30);
 stellen.add(head);
 
 for (int i = 0; i < 5; i++) 
 {
 stellen.add(new Koerper(40, 29 - i));
 }
 
 for (int i = 0; i < 7; i++) 
 {
 stellen.add(new Koerper(40 + i, 24));
 }
 
 Koerper ass = new Koerper(48, 24);
 stellen.add(ass);
 
 }
 
}

public class Spiel 
{
 final int WIDTH = 79;
 final int HEIGHT = 59; 
 int futterx = -1;
 int futtery = -1;
 
 public class Feld 
 {
 boolean bodyon;
 boolean futtern;
 }
 
 Feld[][] spielplatz = new Feld[WIDTH][HEIGHT];
 
 Snake snake;
 
 public Spiel()
 {
 for(int y = 0; y < HEIGHT; y++) 
 {
 for (int x = 0; x < WIDTH; x++) 
 {
 spielplatz[x][y] = new Feld();
 }
 }
 snake = new Snake();
 futterkoord();
 }
 
 private void futterkoord() 
 {
 futterx = (int) (Math.random() * WIDTH - 2);
 futtery = (int) (Math.random() * HEIGHT -2);
 spielplatz[futterx][futtery].futtern = true;
 }
 
 private void futtern() 
 {
 Snake.Koerper kopf = snake.stellen.get(0);
 System.out.println("eat posx ="+kopf.posx+" posy ="+kopf.posy);
 if (spielplatz[kopf.posx][kopf.posy].futtern == true) 
 {
 grow();
 spielplatz[kopf.posx][kopf.posy].futtern = false;
 futterkoord();
 
 }
 }
 private void grow() 
 {
 Snake.Koerper body = snake.stellen.get(snake.stellen.size() -1);
 snake.stellen.add(snake.new Koerper(body.posx, body.posy));
 }
 
 public void play() 
 {
 snake.move();
 futtern();
 }
}

import java.awt.*;
import java.awt.event.*;
public class HFenster extends Frame 

{
 
 public HFenster() 
 {
 super("Sewar Super Snake"); 
 super.addKeyListener(new KeyEvents()); 
 addWindowListener(new WindowAdapter() 
 {
 public void windowClosing(WindowEvent event)
 {
 System.exit(0);
 }
 });
 }
 
 public void update(Graphics g) 
 {
 paint(g);
 }

 public void paint(Graphics g) 
 {
 Ausfuehren.lock.lock();
 g.drawImage(Ausfuehren.display, 0 , 0, null);
 Ausfuehren.lock.unlock();
 }
 
 
 public class KeyEvents extends KeyAdapter 
 {
 public void keyPressed(KeyEvent e)
 {
 
 if (e.getKeyCode() == KeyEvent.VK_UP) 
 {
 if (Ausfuehren.spiel.snake.direction != Snake.DOWN) 
 {
 Ausfuehren.spiel.snake.direction = Snake.UP;
 } 
 }
 
 if (e.getKeyCode() == KeyEvent.VK_DOWN) 
 {
 if (Ausfuehren.spiel.snake.direction != Snake.UP) 
 {
 Ausfuehren.spiel.snake.direction = Snake.DOWN;
 }
 }
 if (e.getKeyCode() == KeyEvent.VK_LEFT) 
 {
 if (Ausfuehren.spiel.snake.direction != Snake.RIGHT) 
 {
 Ausfuehren.spiel.snake.direction = Snake.LEFT;
 }
 }
 if (e.getKeyCode() == KeyEvent.VK_RIGHT) 
 {
 if (Ausfuehren.spiel.snake.direction != Snake.LEFT) 
 {
 Ausfuehren.spiel.snake.direction = Snake.RIGHT;
 }
 }
 }
 }
}