need help

public class MyKaraIO extends KaraIO {
    int pos1,pos2;
    /**
     * In the 'act()' method you can write your program for Kara <br>
     * <i>In der Methode 'act()' koennen die Befehle fuer Kara programmiert werden</i>
     */
    public void act() {
        int pos = 0,x = 0; String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
        for(int i = 0;i < 26;i++) {
            char ltd = alphabet.charAt(pos);
            Map<Character,Letter> letterMap = new HashMap<Character,Letter>();  letterMap.put(ltd, new Letter(pos, ltd));
            getWorld().addObject(letterMap.get(ltd),x,3); pos ++; x ++;
        }
        Greenfoot.delay(1);
        pos1 = alphabet.indexOf(JOptionPane.showInputDialog("Bitte einen Buchstaben von A-Z!").toUpperCase()); pos2 = (int)(26*Math.random()); 
        if(pos1 < pos2) {
            getWorld().showText("zu klein!",5,5);
            for(int i = 0;i <= pos1;i++) {
                Letter ltd = (Letter) getWorld().getObjectsAt(i, 3, Letter.class);
                getWorld().removeObject(ltd);
            }
        } else if(pos1 > pos2) {
             getWorld().showText("zu Groß!",5,5);
            for(int i = 25;i >= pos1;i--) {
                Letter ltd = (Letter) getWorld().getObjectsAt(i, 3, Letter.class);
                getWorld().removeObject(ltd);
            }
        }
    }

}

public class Letter extends Actor
{

    int i;
    public Letter (int alphabet, char letter) {
        i = alphabet; setImage(new GreenfootImage(""+letter,25 ,Color.BLACK, new Color(0,0,0,0)));
    }
}