public class CrabWorld extends World
{
    static int xDimension = 800;        // X Dimension of our World
    static int yDimension = 800;        // Y Dimension of our World
    
    static int minWorms = 8;
    static int maxWorms = 10;
    static int numWorms = Greenfoot.getRandomNumber(minWorms - maxWorms);
    
    /**
     * Create the crab world (the beach). Our world has a size 
     * of xDimension x yDimension cells, where every cell is just 1 pixel.
     */
    public CrabWorld() 
    {
        super(xDimension, yDimension, 1);
        
        // Populuate with a Crab in the the center of my world
        int crabXPosition = xDimension/2;
        int crabYPosition = yDimension/2;
        
        // Add my crab
        populateCrab(crabXPosition, crabYPosition);
        
        // Add some worms
        populateWorms(numWorms);
    }
    
    /**
     * Place a crab in the world at xPosition and yPosition
     */
    private void populateCrab(int xPosition, int yPosition)
    {
        addObject(new Crab(), xPosition, yPosition);
    }
    
     /**
     * Place specified number of worms randomly in the world
     */
    private void populateWorms(int numberOfWorms)
    {
        int loopNumber = 0;
        
        while (loopNumber < numberOfWorms) {
            // add a worm to the world, at a random location
            addObject(new Worm(), Greenfoot.getRandomNumber(xDimension), Greenfoot.getRandomNumber(yDimension)); 
            
            loopNumber++;
        }
    }
}