Fire.java

package model;

import util.Position;
import java.util.*;

public class Fire {
    public static List<Position> firePositions;
     
    public static void nextMove(){
        // propagate the fire to the adjacent cells
        List<Position> newFirePositions = new ArrayList<>();
        for (Position firePosition : firePositions) {
            List<Position> neighborPositions = Utils.neighbors(firePosition);
            newFirePositions.addAll(neighborPositions);
        }
        // check if the new fire positions are not already on fire
        for (Position newFirePosition : newFirePositions)
            if (!firePositions.contains(newFirePosition))
                firePositions.add(newFirePosition);
    }
}