abstract class Entity { 
  public Location location = new Location(0,0);
  public abstract void move(int x, int y); 
  public boolean isAt(int x, int y){
    return this.location.getX() == x && this.location.getY() == y;
  }
}
class Treasure extends Entity {
  public void move(int x, int y){ } //Doesn't move 
}