Mine

import info.gridworld.actor.Actor;
import info.gridworld.actor.Critter;
import info.gridworld.grid.Grid;
import info.gridworld.grid.Location;
import info.gridworld.actor.Rock;

import java.awt.Color;
import java.util.ArrayList;

public class RockHound extends Critter
{
	public void processActors(ArrayList<Actor> actors)
	{
		for(Actor a : actors)
		{
			if((a instanceof Rock) && !(a instanceof Critter))
				a.removeSelfFromGrid();
		}
	}	
}