Java Programming

I am trying to use the following code to detect if an explosion is on top of a brick:

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

/**
 * Write a description of class redexplosion here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class redexplosion extends explosion
{
    int explosionTime = 100;
    /**
     * Act - do whatever the explosions wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        explosionTime--;
        checkExplosion();
    }    
    
    private void checkExplosion()
    {
        if(explosionTime == 0)
        {
            getWorld().removeObject(this);
        }
        Actor brick = getOneIntersectingObject(brick.class); 
        //if(brick != null)
        //{ 
        //    getWorld().removeObject(brick);
        //}
    }   
}

But it keeps giving me this error:

java.lang.IllegalStateException: The actor has not been inserted into a world so it has no location yet. You might want to look at the method addedToWorld on the Actor class.
	at greenfoot.Actor.failIfNotInWorld(Actor.java:605)
	at greenfoot.Actor.getOneIntersectingObject(Actor.java:750)
	at redexplosion.checkExplosion(redexplosion.java:29)
	at redexplosion.act(redexplosion.java:20)
	at greenfoot.core.Simulation.runOneLoop(Simulation.java:199)
	at greenfoot.core.Simulation.run(Simulation.java:128)

I see examples like this all the time but this one has me stumped. The brick clas name is lowercase so it isn't caused by that - capitalizing actually gives me a class not found error.