Removing objects

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

/**
 * Write a description of class Spawner here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Spawner extends Actor
{
    /**
     * Act - do whatever the Spawner wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    World world=(MyWorld) getWorld();
    public int zombies2kill = 5;
    public int zombieskilled = 0;
    public int zombies2spawn = 0;
    private int delay = 0;
    
    
    public void act() 
    {
        if(delay > 0){
            delay--;
        }
        
        if (zombieskilled == zombies2kill)victory();
            
            
       
        
        if(delay == 0 && zombies2spawn < zombies2kill) spawn();
        
    }    
    private void victory(){
        Actor Guy;
        Guy = getOneObjectAtOffset(0,0, Guy.class);
        if (Guy == null){
        getWorld().removeObject(Guy);
    }
    }
    private void spawn(){
        
        int lr = Greenfoot.getRandomNumber(3);
        if(lr==2){
            Green2 green2 = new Green2();
            getWorld().addObject(green2,580,380);
            zombies2spawn++;
            delay = 80;
        }
        if(lr==1){
            Green green = new Green();
            getWorld().addObject(green,0,380);
            zombies2spawn++;
            delay = 80;
        }
        
    }
    
    }