Where is my error

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

/**
 * Write a description of class Astroid here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Missile extends Objects {
    Scoreboard Scoreboard;
   boolean touchingMissile;
    public Missile(Scoreboard pointScoreboard) {
        Scoreboard = pointScoreboard;
    }

    public void act() {
        movement();
        makeMissile();
        removeMissile();
    }

    /**
     * The movement and rotation for the missile.
     */
    private void movement() {
        int x = getX() -3;
        int y = getY();
        setLocation(x, y);
    }

    /**
     * If the missile is at the edge of the world or is hit by a bullet shot
     * it will be removed and it will create a new missile. Also randomly
     * creates missile
     */
    public void makeMissile() {
        World world = getWorld();
        Missile newMissile = new Missile(Scoreboard);
        int worldHeight = world.getHeight();
        int worldWidth = world.getWidth();
        if(Greenfoot.getRandomNumber(9999) < 9) {
            world.addObject(newMissile, worldWidth, Greenfoot.getRandomNumber(worldHeight));
        }
    }

    public void removeMissile() {
        World world = getWorld();
        Missile newMissile = new Missile(Scoreboard);
        int worldHeight = world.getHeight();
        int worldWidth = world.getWidth();
        if(atWorldEdge()&& this != null) {
            world.removeObject(this);
            world.addObject(newMissile, worldWidth, Greenfoot.getRandomNumber(worldHeight));
        }
        if(onContact(Bullet.class) && this != null) {
            Scoreboard.add(100);
            world.removeObject(this);
            world.addObject(newMissile, worldWidth, Greenfoot.getRandomNumber(worldHeight));
        }
    }
}