public void showMainMenu() {
        while (true) {
            System.out.println("~~~~~~~~~~数据库管理系统~~~~~~~~~~");
            System.out.println("1、添加用户");
            System.out.println("2、删除用户");
            System.out.println("3、更改用户");
            System.out.println("4、查询所有用户");
            System.out.println("5、退出");
            int choose;
            Scanner scanner = new Scanner(System.in);
            if (scanner.hasNextInt()) {
                choose = scanner.nextInt();
                switch (choose) {
                    case 1:
                        viewController.insert(employerDAO);
                        break;
                    case 2:
                        viewController.delete(employerDAO);
                        break;
                    case 3:
                        viewController.update(employerDAO);
                        break;
                    case 4:
                        viewController.select(employerDAO);
                        break;
                    case 5:
                        if (methodPool.close()) {
                            System.exit(0);
                        }else{
                            System.out.println("非正常退出");
                            System.exit(0);
                        }

                        break;
                }
            }
        }
    }