Snake

public class MyWorld extends World
{
    Snake snake = new Snake();
    
    private int xVel = 5;
    private int yVel = 2;
    private int speed = 2;
    
    /**
     * Constructor for objects of class MyWorld.
     * 
     */
    public MyWorld() {    
        // Create a new world with 600x400 cells with a cell size of 1x1 pixels.
        super(900, 600, 1);
        snake.setImage(new GreenfootImage("smiley1.png"));
        addObject(snake, 1, 0);
        addBodySegment(0, 0, snake);
    }
    
    private void addBodySegment(int xLoc, int yLoc, Snake leader) {
        Snake body = new Snake();
        leader.setFollower(body);
        addObject(body, xLoc, yLoc);
    }
    
     public void act() {
        moveAndGrow();
        wallCollision();
    }
    
    private void moveAndGrow() {
        int atX = snake.getX();
        int atY = snake.getY();
        
        Snake body = snake;
        moveSnakeHead();
        
        while(body.getFollower() != null) {
            body = body.getFollower();
            int newX = body.getX();
            int newY = body.getY();
            body.setLocation(atX, atY);
            atX = newX;
            atY = newY;
        }
        
        if (Greenfoot.getRandomNumber(100) < (10))
            addBodySegment(atX, atY, body);
    }
    
    private void moveSnakeHead() {        
        snake.setLocation(snake.getX()+(xVel+speed), snake.getY()+(yVel+speed));
    }
    
    public void wallCollision() {
        if (snake.getX() < 40 || snake.getX() > 860) {
            xVel = -xVel;
        }
    
        if (snake.getY() < 40 || snake.getY() > 560) {
            yVel = -yVel;
        }
    }
    
}