Help game bar

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
import java.awt.Color; //Java Color class
/**
 * Counts up in seconds and increases a bars height when
 * a key is pressed down. If the key is released the bar falls
 * back to zero. If the count reaches the duration the bar
 * and count remain there.
 * 
 * @author Michael Clapham
 * @version v1.0
 */
public class CounterBar  extends Actor
{
    private long startTime; //The system time we started counting in miliseconds
    private long count = -1; //The number of miliseconds since we started counting
    private long duration = 4000; //The number of miliseconds needed to fill the bar
    private boolean finished = false;//This is set to true once the bar reaches a certain length
    private int barMaxHeight = 80;//The max height the bar can reach
    private String keyString = "a";//The key that is pressed down to increase the count
    private Color barColor = Color.RED;
    private Color textColor = Color.MAGENTA;
    
    /**
     * Constructor for CounterBar objects. This paints the bar when it is created
     */
    public CounterBar(){
        paint();
    }
    
    /**
     * Act - do whatever the CounterBar wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        if(Greenfoot.isKeyDown(keyString)){
            if(count == -1){
                //If the count is -1 we have only just started counting so we take the
                //start time in MILISECONDS
                startTime = System.currentTimeMillis();
            }
            //We set the count to the difference between the current time and the start time
            count = System.currentTimeMillis() - startTime;
        } else {
            count = -1;
        }
        paint();
    }    
    
    /**
     * Paints the bar and counter
     */
    public void paint(){
        //Creates a new GreenfootImage with width 20 and height 100
        GreenfootImage img = new GreenfootImage(20,100);
        
        //Calculates the height of the bar
        int barHeight = (int) (barMaxHeight * count / duration);
        //If the height is greater than the max height we are finished
        if(barHeight > barMaxHeight-2){
            finished = true;
        }
        if(finished){
            //If we are finished we draw the bar filled
            img.setColor(barColor);
            img.fillRect(0,0,20,barMaxHeight);
            //And the duration in seconds is drawn as the timer text
            img.setColor(textColor);
            img.drawString("" + (duration/1000), 8, 90);
        } else {
            //Else we draw the bar starting in the top left corner (0,0) with a width of 20
            //and a height that we calculated before.
            img.setColor(barColor);
            img.fillRect(0,0,20,barHeight);
            //We then draw the count divided by 1000 to give it in seconds rather
            //than miliseconds
            img.setColor(textColor);
            img.drawString("" + (count/1000), 4, 90);
        }
        //We then set the image we just painted on, to be the Actors image.
        setImage(img);
    }
}