Exception beim löschen verhindern ?

import java.util.ArrayList;

import org.newdawn.slick.AppGameContainer;
import org.newdawn.slick.BasicGame;
import org.newdawn.slick.Color;
import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.Image;
import org.newdawn.slick.Input;
import org.newdawn.slick.SlickException;

public class Cardrive extends BasicGame {

	private Image bg; // Attribut für das Hintergrundbild
	private ArrayList<Car> autos = new ArrayList<Car>(); 

															
	private Player player; // Der Spieler

	private int neuesAutoTimer = 0;
	private boolean gameOver = false; // Die GameOver Variable
	private Input input; // Spieler Input

	@Override
	public void init(GameContainer gc) throws SlickException {
		bg = new Image("bg.png"); 
		player = new Player(gc.getInput()); 
		input = gc.getInput();
	}

	@Override
	public void update(GameContainer gc, int delta) throws SlickException {

		neuesAutoTimer += delta;

		player.bewegen(delta);

		if (neuesAutoTimer >= 750 && gameOver == false) {

			autos.add(new Car((int) (Math.random() * (2 - 0) + 0)));

			neuesAutoTimer = 0;

		}

		for (Car auto_now : autos) {
			auto_now.bewegen(delta);
		}

		if (autos.size() > 0 ) {

			for (Car auto_now : autos) {
				if (player.getHitbox().intersects(auto_now.getHitbox())) {

					autos.remove(auto_now);

					gameOver = true;

				}
			}
		}

		if (input.isKeyPressed(Input.KEY_ENTER) && gameOver == true) {

			autos.clear();
			neuesAutoTimer = 0;
			gameOver = false;

		}

	}

	@Override
	public void render(GameContainer gc, Graphics gfx) throws SlickException {

		// Der Hintergrund wird gezeichnet
		bg.draw();

		// Alle Autos in der Liste werden gezeichnet
		for (int i = 0; i < autos.size(); i++) {
			Car auto = autos.get(i);
			auto.zeichnen();
			gfx.draw(auto.getHitbox());
		}

		// Den Spieler mit der Hitbox zeichen
		player.zeichnen();
		gfx.draw(player.getHitbox());

		// Anzeige für den momentanen delta-Wert
		gfx.drawString("delta: " + neuesAutoTimer, 25, 50);

		// Anzeige für die momentanen Autos auf dem Bildschirm
		gfx.drawString("Autos: " + autos.size(), 25, 75);

		// Gameover anzeigen
		if (gameOver) {
			gfx.setColor(Color.red);
			gfx.drawString(
					"Du hast verloren!! \nDrücke Enter für einen Neustart!",
					200, 300);
		} else {
			gfx.setColor(Color.white);
		}
	}

	public Cardrive(String title) {
		super(title);

	}

	public static void main(String[] args) throws SlickException {
		AppGameContainer myGame = new AppGameContainer(
				new Cardrive("Car Drive"));
		myGame.setDisplayMode(600, 800, false);

		myGame.start();
	}

}

Sun Jan 11 14:11:15 CET 2015 ERROR:null
java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at Cardrive.update(Cardrive.java:64)
	at org.newdawn.slick.GameContainer.updateAndRender(GameContainer.java:663)
	at org.newdawn.slick.AppGameContainer.gameLoop(AppGameContainer.java:411)
	at org.newdawn.slick.AppGameContainer.start(AppGameContainer.java:321)
	at Cardrive.main(Cardrive.java:129)
Sun Jan 11 14:11:15 CET 2015 ERROR:Game.update() failure - check the game code.
org.newdawn.slick.SlickException: Game.update() failure - check the game code.
	at org.newdawn.slick.GameContainer.updateAndRender(GameContainer.java:669)
	at org.newdawn.slick.AppGameContainer.gameLoop(AppGameContainer.java:411)
	at org.newdawn.slick.AppGameContainer.start(AppGameContainer.java:321)
	at Cardrive.main(Cardrive.java:129)

Iterator<E> it = list.iterator();
while (it.hasNext()) { E obj = it.next(); }

for (Car auto_now : autos) {
	if (player.getHitbox().intersects(auto_now.getHitbox())) {
           autos.remove(auto_now);
           gameOver = true;
        }
}

Iterator<Car> it = autos.iterator();
while (it.hasNext()) {
   Car auto_now = it.next();
   if (player.getHitbox().intersects(auto_now.getHitbox())) {
       it.remove();
       gameOver = true;
   }
}

for(Iterator<Car> it = autos.iterator(); it.hasNext(); ) {
    Car auto_now = it.next();
    if (player.getHitbox().intersects(auto_now.getHitbox())) {
        it.remove();
        gameOver = true;
    }
}