public class Main {
    public static void main (String[] args) {

        SafetyCheckVisitor safetyVisitor = new SafetyCheckVisitor();
        MaintenanceVisitor maintenanceVisitor = new MaintenanceVisitor();

        Wheel wheel = new Wheel();
        Engine engine = new Engine();

        wheel.accept(safetyVisitor);
        wheel.accept(maintenanceVisitor);
        engine.accept(safetyVisitor);
        engine.accept(maintenanceVisitor);

    }
}