int randomNum = 1 + Greenfoot.getRandomNumber(119);

int counter = 0;

public void act()
{
counter++;
removeCherry();
}

public void removeCherry()
{
    if (counter == 300) // the act method is called 30 times a second, 300 = 10 seconds.
    {
       getWorld().removeObject(yourobject);
    }
}

// the act method is called 30 times a second, 300 = 10 seconds.

if (counter == 300)

if (counter == 600)

if (counter == 620)

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

/**
 * Write a description of class Kirsche here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */

public class Kirsche extends Actor
{
    private int counter;
    /**
     * Act - do whatever the Kirsche wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void Kirsche()
    {
         counter = 0;
    }
     public void act()
    { 
        counter++;
        removeCherry();  
        int randomNum = 1 + Greenfoot.getRandomNumber(119);
    }
     
     public void removeCherry()  
    {  
        if (counter == 620) // the act method is called 30 times a second, 300 = 10 seconds.  
        {  
             getWorld().removeObject(Kirsche.class);
        }  
    } 
    

}

getWorld().removeObject(this);

getWorld().removeObject(Kirsche.class);

int randomNum = 1 + Greenfoot.getRandomNumber(119);  

int x = Greenfoot.getRandomNumber(getWorld().getWidth());
int y = Greenfoot.getRandomNumber(getWorld().getHeight());
setLocation(x,y);

int x = Greenfoot.getRandomNumber(getWorld().getWidth());
int y = Greenfoot.getRandomNumber(getWorld().getHeight());
if (getObjects(Actor.class, x, y).isEmpty())
    setLocation(x,y);

int randomNum = 1 + Greenfoot.getRandomNumber(119);

if (randomNumber > 0)
{
    randomNumber--;
    if (randomNumber == 0)
    {
        addObject(new Kirsche(), 'x-location', 'y-location');
    }
}