Counter Problem

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
import java.awt.Color;

/**
 * A Counter class that allows you to display a numerical value on screen.
 * 
 * The Counter is an actor, so you will need to create it, and then add it to
 * the world in Greenfoot.  If you keep a reference to the Counter then you
 * can adjust its value.  Here's an example of a world class that
 * displays a counter with the number of act cycles that have occurred:
 * 
 * <pre>
 * class CountingWorld
 * {
 *     private Counter actCounter;
 *     
 *     public CountingWorld()
 *     {
 *         super(600, 400, 1);
 *         actCounter = new Counter("Act Cycles: ");
 *         addObject(actCounter, 100, 100);
 *     }
 *     
 *     public void act()
 *     {
 *         actCounter.setValue(actCounter.getValue() + 1);
 *     }
 * }
 * </pre>
 * 
 * @author Neil Brown and Michael Kölling 
 * @version 1.0
 */
public class Counter extends Actor
{
    private static final Color transparent = new Color(0,0,0,0);
    private GreenfootImage background;
    private int value;
    private int target;
    private String prefix;
    
    public Counter()
    {
        this(new String());
    }

    /**
     * Create a new counter, initialised to 0.
     */
    public Counter(String prefix)
    {
        background = getImage();  // get image from class
        value = 0;
        target = 0;
        this.prefix = prefix;
        updateImage();
    }
    
    /**
     * Animate the display to count up (or down) to the current target value.
     */
    public void act() 
    {
        if (value < target) {
            value++;
            updateImage();
        }
        else if (value > target) {
            value--;
            updateImage();
        }
    }

    /**
     * Add a new score to the current counter value.  This will animate
     * the counter over consecutive frames until it reaches the new value.
     */
    public void add(int score)
    {
        target += score;
    }

    /**
     * Return the current counter value.
     */
    public int getValue()
    {
        return target;
    }

    /**
     * Set a new counter value.  This will not animate the counter.
     */
    public void setValue(int newValue)
    {
        target = newValue;
        value = newValue;
        updateImage();
    }
    
    /**
     * Sets a text prefix that should be displayed before
     * the counter value (e.g. "Score: ").
     */
    public void setPrefix(String prefix)
    {
        this.prefix = prefix;
        updateImage();
    }

    /**
     * Update the image on screen to show the current value.
     */
    private void updateImage()
    {
        GreenfootImage image = new GreenfootImage(background);
        GreenfootImage text = new GreenfootImage(prefix + value, 22, Color.BLACK, transparent);
        
        if (text.getWidth() > image.getWidth() - 20)
        {
            image.scale(text.getWidth() + 20, image.getHeight());
        }
        
        image.drawImage(text, (image.getWidth()-text.getWidth())/2, 
                        (image.getHeight()-text.getHeight())/2);
        setImage(image);
    }
}

import greenfoot.*;  // (World, Actor, GreenfootImage, and Greenfoot)
import java.awt.Color;

/**
 * Space. Something for rockets to fly in.
 * 
 * @author Michael Kolling
 * @version 1.0
 */
public class Space extends World
{
    private Counter scoreCounter1;
    private Counter scoreCounter2;
    private Counter scoreCounter3;
    private Counter scoreCounter4;
    private int startAsteroids = 3;

    //Space station goes across screen.

    public Space() 
    {
        super(600, 400, 1);
        GreenfootImage background = getBackground();
        background.setColor(Color.BLACK);
        background.fill();

        Rocket rocket = new Rocket();
        addObject(rocket, getWidth()/2 + 100, getHeight()/2);

        addAsteroids(startAsteroids);

        scoreCounter1 = new Counter("Score: 0");
        addObject(scoreCounter1, 60, 380);

        scoreCounter2 = new Counter("Fuel: 500");
        addObject(scoreCounter2, 60, 20);

        scoreCounter3 = new Counter("Bullets: 100");
        addObject(scoreCounter3, 540, 20);

        scoreCounter4 = new Counter("Health: 5");
        addObject(scoreCounter4, 540, 380);

        Explosion.initializeImages();
        ProtonWave.initializeImages();
    }

    
         
         

    public void act()
    {
        addSpaceStations();
        scoreCounter1.setValue(scoreCounter1.getValue() + 1);

    }

    public void addSpaceStations()
    {
        if(Greenfoot.getRandomNumber(200)==1){
            addObject(new SpaceStation(),getWidth()/2, getHeight()/2);
        }
    }

    /**
     * Add a given number of asteroids to our world. Asteroids are only added into
     * the left half of the world.
     */
    private void addAsteroids(int count) 
    {
        for(int i = 0; i < count; i++) 
        {
            int x = Greenfoot.getRandomNumber(getWidth()/2);
            int y = Greenfoot.getRandomNumber(getHeight()/2);
            addObject(new Asteroid(), x, y);
        }
    }

    /**
     * This method is called when the game is over to display the final score.
     */
    public void gameOver() 
    {
        // TODO: show the score board here. Currently missing.
    }

}