public static void main(String[] args) {
        // ǵĽͷ
        Invoker xiaoSan = new Invoker(); // ͷ˾С
        // ͻҪһ
        System.out.println("-------------ͻҪһ-----------------");
        // ͻ
//        Command command = new AddRequirementCommand();
        Command command = new DeletePageCommand();
        // ͷ˽յ
        xiaoSan.setCommand(command);
        // ͷִ
        xiaoSan.action();
    }