public void putGameCharacter(GameCharacter mob, Position pos) {
getCell(pos).setGameCharacter(mob);
mob.setPositionOnMap(new PositionOnMap(pos, this));
}
public void removeGameCharacter(GameCharacter mob) {
Preconditions.checkState(mob.getMap().equals(this));
MapCell cell = getCell(mob.getPosition());
mob.setPositionOnMap(null);
cell.setGameCharacter(null);
}