Move the snake

public void addedToWorld(World world)
{
    if (!"head".equals(segment)) return;
    counter = new Counter(); // may have to adjust constructor call
    world.addObject(counter, 100, 100); //wherever
}

getWorld().removeObjects(getWorld().getObjects(null));

if (getWorld() == null) return;

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
/**
 * Write a description of class Playground here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Playground extends World
{
    /**
     * Defines the variables required in game.
     */
    private Snake snakeBody[];
    private Food food;
    private Counter score;
    private int direction;
    private boolean eaten;
    private int gameState;
    /**
     * Constructor for objects of class Playground.
     * 
     */
    public Playground()
    {    
        // Create a new world with 600x400 cells with a cell size of 1x1 pixels.
        super(600, 400, 1); 
        direction = 0;
        eaten = false;
        gameState = 0;
    }

    /**
     * Game starts from here.
     */ 
    public void act()
    {
        checkKeys();
        gameStates();
        
        if(eaten)
        {
            updateFoodLocation();// updates the location of the food;
        }


        int previousLocationX = snakeBody[0].getX();
        int previousLocationY = snakeBody[0].getY();
        snakeBody[0].move(20); // moves one step

        
        if(snakeBody[0].getX()!=previousLocationX || snakeBody[0].getY()!=previousLocationY) // Checks if the snake hits walls
        {
            for(int i=1; i<snakeBody.length; i++)
            {
                previousLocationX = snakeBody[i].getX();
                previousLocationY = snakeBody[i].getY();
                snakeBody[i].move(20); // entire body moves one step

            }

            if(snakeBody[0].getX()==food.getX() && snakeBody[0].getY()==food.getY()) // Checks if the snake eats food
            {
                growSnake(previousLocationX, previousLocationY);
                updateFoodLocation();
                score.add(5);
            }

            for ( int i = 1; i < snakeBody.length; i++)// Checks if the snake eats itself
            {
                if( snakeBody[0].getX() == snakeBody[i].getX() && 
                snakeBody[0].getY() == snakeBody[i].getY());
                {
                    gameState = -1;
                }
            }
        }
        else
        {
            gameState = -1;
        }
    }

    /**
     * This method will update the length of the Snake.
     */
    private void growSnake(int x, int y)
    {
        Snake s = new Snake(false);
        Snake oldSnake[] = new Snake[snakeBody.length];
        for(int i = 0; i < snakeBody.length; i++)
        {
            oldSnake[i] = snakeBody[i];
        }
        snakeBody = new Snake[snakeBody.length+1];
        for( int i = 0; i < snakeBody.length -1; i++)
        {
            snakeBody[i] = oldSnake[i];
        }
        snakeBody[snakeBody.length-1] = s;
        addObject(snakeBody[snakeBody.length-1], x , y);
    }

    private void updateFoodLocation()
    {
        int x = 0;
        int y = 0;
        boolean overlap = true;
        eaten = false;

        while(overlap)
        {
            x = Greenfoot.getRandomNumber(getWidth());
            y = Greenfoot.getRandomNumber(getHeight());

            for( int i = 1; i < snakeBody.length; i++)
            {
                // Condition to check food will not touch the snake
                if( x!= snakeBody[i].getX() || y!=snakeBody[i].getY())
                {
                    overlap = false;
                    break;
                }
            }
        }
        food.setLocation(x * 15, y * 15);
    }

    public void checkKeys()
    {
        if(Greenfoot.isKeyDown("right")) // checks if right key is pressed
        {
            if(direction==1 || direction==3)
                direction = 0;
        }
        else if(Greenfoot.isKeyDown("down")) // checks if down key is pressed
        {
            if(direction==0 || direction==2)
                direction = 1;
        }
        else if(Greenfoot.isKeyDown("left")) // checks if left key is pressed
        {
            if(direction==1 || direction==3)
                direction = 2;
        }
        else if(Greenfoot.isKeyDown("up")) // checks if up key is pressed
        {
            if(direction==0 || direction==2)
                direction = 3;
        }
    }
    
    public void gameStates()
    {
        if( gameState==0) // Initialization
        {
            setBackground("SnakeGame.jpg");
        }
        if(Greenfoot.getKey() !=null) // check if any key is pressed
        {
            gameState = 1; return;
        }
        else if ( gameState == 1) // Game Activate State
        {
            setBackground("bluerock.jpg");

            food = new Food(); // initialization of the food
            addObject(food, 0,0); // adding food actor to the world

            score = new Counter("Score : "); // initialization of the score
            addObject( score, 20, 4);// adding score

            snakeBody = new Snake[3]; // // initialization of the Snake
            for( int i = 0; i < snakeBody.length; i++)
            {
                snakeBody[i] = new Snake(i==0);
                addObject(snakeBody[i], 90+(snakeBody.length-i)* 15, 30);
            }
            updateFoodLocation();
            gameState = 2;
            return;
        }

        else if( gameState == -1) // game over
        {

            setBackground("GameOver.jpg");
            addObject(score, 300, 8);
            return;
        }
    }
}