帮我写一个 java 的员工信息管理系统 用switch展示菜单 持久化数据

好的，以下是一个简单的Java员工信息管理系统的代码，使用了switch展示菜单和文件持久化数据：

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class EmployeeManagementSystem {

    private List<Employee> employees;
    private static final String FILE_PATH = "employees.txt";

    public EmployeeManagementSystem() {
        employees = new ArrayList<>();
    }

    public void start() {
        System.out.println("Welcome to Employee Management System!");
        loadEmployees(); // 加载员工数据

        Scanner scanner = new Scanner(System.in);
        boolean quit = false;

        while (!quit) {
            System.out.println("\nPlease select an option:");
            System.out.println("1. Add an employee");
            System.out.println("2. Update an employee");
            System.out.println("3. Remove an employee");
            System.out.println("4. View all employees");
            System.out.println("5. Quit");

            int choice = scanner.nextInt();
            scanner.nextLine();

            switch (choice) {
                case 1:
                    addEmployee(scanner);
                    break;
                case 2:
                    updateEmployee(scanner);
                    break;
                case 3:
                    removeEmployee(scanner);
                    break;
                case 4:
                    viewEmployees();
                    break;
                case 5:
                    quit = true;
                    break;
                default:
                    System.out.println("Invalid choice, please try again.");
                    break;
            }
        }

        saveEmployees(); // 保存员工数据
        System.out.println("Goodbye!");
    }

    private void addEmployee(Scanner scanner) {
        System.out.println("\nPlease enter the employee ID:");
        int id = scanner.nextInt();
        scanner.nextLine();

        System.out.println("Please enter the employee name:");
        String name = scanner.nextLine();

        System.out.println("Please enter the employee age:");
        int age = scanner.nextInt();
        scanner.nextLine();

        System.out.println("Please enter the employee department:");
        String department = scanner.nextLine();

        Employee employee = new Employee(id, name, age, department);
        employees.add(employee);
        System.out.println("Employee added successfully.");
    }

    private void updateEmployee(Scanner scanner) {
        System.out.println("\nPlease enter the employee ID to update:");
        int id = scanner.nextInt();
        scanner.nextLine();

        Employee employee = findEmployeeById(id);
        if (employee != null) {
            System.out.println("Please enter the employee name:");
            String name = scanner.nextLine();
            employee.setName(name);

            System.out.println("Please enter the employee age:");
            int age = scanner.nextInt();
            scanner.nextLine();
            employee.setAge(age);

            System.out.println("Please enter the employee department:");
            String department = scanner.nextLine();
            employee.setDepartment(department);

            System.out.println("Employee updated successfully.");
        } else {
            System.out.println("Employee not found.");
        }
    }

    private void removeEmployee(Scanner scanner) {
        System.out.println("\nPlease enter the employee ID to remove:");
        int id = scanner.nextInt();
        scanner.nextLine();

        Employee employee = findEmployeeById(id);
        if (employee != null) {
            employees.remove(employee);
            System.out.println("Employee removed successfully.");
        } else {
            System.out.println("Employee not found.");
        }
    }

    private void viewEmployees() {
        System.out.println("\nEmployee List:");
        for (Employee employee : employees) {
            System.out.println(employee);
        }
    }

    private Employee findEmployeeById(int id) {
        for (Employee employee : employees) {
            if (employee.getId() == id) {
                return employee;
            }
        }
        return null;
    }

    private void loadEmployees() {
        try (BufferedReader reader = new BufferedReader(new FileReader(FILE_PATH))) {
            String line = null;
            while ((line = reader.readLine()) != null) {
                String[] fields = line.split(",");
                int id = Integer.parseInt(fields[0]);
                String name = fields[1];
                int age = Integer.parseInt(fields[2]);
                String department = fields[3];
                Employee employee = new Employee(id, name, age, department);
                employees.add(employee);
            }
            System.out.println("Employee data loaded successfully.");
        } catch (FileNotFoundException e) {
            System.out.println("Employee data file not found, starting with empty data.");
        } catch (IOException e) {
            System.out.println("Error while reading employee data file.");
        }
    }

    private void saveEmployees() {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(FILE_PATH))) {
            for (Employee employee : employees) {
                writer.write(employee.getId() + "," + employee.getName() + "," + employee.getAge() + ","
                        + employee.getDepartment());
                writer.newLine();
            }
            System.out.println("Employee data saved successfully.");
        } catch (IOException e) {
            System.out.println("Error while writing employee data file.");
        }
    }

    public static void main(String[] args) {
        EmployeeManagementSystem system = new EmployeeManagementSystem();
        system.start();
    }

}

在该示例中，我们定义了一个EmployeeManagementSystem类，其中包含了添加、更新、删除和查看员工信息的方法。在start方法中，我们使用switch语句展示菜单，根据用户选择调用相应的方法。在程序启动和退出时，我们分别调用loadEmployees和saveEmployees方法，从文件中加载员工数据，或将员工数据保存到文件中。

需要注意的是，该示例中的员工数据仅包含了ID、姓名、年龄和部门信息，实际项目中需要根据需求进行扩展。此外，我们还需要考虑员工数据的索引、查询等功能，以提高系统的查询和操作效率。