用java写.List： 员工管理系统 员工属性：员工编号、员工姓名、性别、年龄、所在部门 1————员工添加 2————员工删除 3————员工信息修改 4————根据员工编号查询员工信息 5————查询所有员工信息

好的，以下是一个基本的员工管理系统的Java实现，包含了员工添加、删除、修改和查询等功能：

import java.util.ArrayList;
import java.util.Scanner;

public class EmployeeManagementSystem {
    private static ArrayList<Employee> employees = new ArrayList<>();

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 员工添加");
            System.out.println("2. 员工删除");
            System.out.println("3. 员工信息修改");
            System.out.println("4. 根据员工编号查询员工信息");
            System.out.println("5. 查询所有员工信息");
            System.out.println("0. 退出系统");
            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    addEmployee();
                    break;
                case 2:
                    deleteEmployee();
                    break;
                case 3:
                    updateEmployee();
                    break;
                case 4:
                    queryEmployeeById();
                    break;
                case 5:
                    queryAllEmployees();
                    break;
                case 0:
                    System.out.println("谢谢使用！");
                    System.exit(0);
                default:
                    System.out.println("输入有误，请重新选择！");
                    break;
            }
        }
    }

    private static void addEmployee() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入员工编号：");
        String id = scanner.nextLine();
        System.out.println("请输入员工姓名：");
        String name = scanner.nextLine();
        System.out.println("请输入员工性别：");
        String gender = scanner.nextLine();
        System.out.println("请输入员工年龄：");
        int age = scanner.nextInt();
        scanner.nextLine();
        System.out.println("请输入员工所在部门：");
        String department = scanner.nextLine();
        employees.add(new Employee(id, name, gender, age, department));
        System.out.println("添加成功！");
    }

    private static void deleteEmployee() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入要删除的员工编号：");
        String id = scanner.nextLine();
        for (Employee employee : employees) {
            if (employee.getId().equals(id)) {
                employees.remove(employee);
                System.out.println("删除成功！");
                return;
            }
        }
        System.out.println("员工编号不存在，删除失败！");
    }

    private static void updateEmployee() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入要修改的员工编号：");
        String id = scanner.nextLine();
        for (Employee employee : employees) {
            if (employee.getId().equals(id)) {
                System.out.println("请输入员工姓名（留空表示不修改）：");
                String name = scanner.nextLine();
                if (!name.isEmpty()) {
                    employee.setName(name);
                }
                System.out.println("请输入员工性别（留空表示不修改）：");
                String gender = scanner.nextLine();
                if (!gender.isEmpty()) {
                    employee.setGender(gender);
                }
                System.out.println("请输入员工年龄（留空表示不修改）：");
                String ageStr = scanner.nextLine();
                if (!ageStr.isEmpty()) {
                    int age = Integer.parseInt(ageStr);
                    employee.setAge(age);
                }
                System.out.println("请输入员工所在部门（留空表示不修改）：");
                String department = scanner.nextLine();
                if (!department.isEmpty()) {
                    employee.setDepartment(department);
                }
                System.out.println("修改成功！");
                return;
            }
        }
        System.out.println("员工编号不存在，修改失败！");
    }

    private static void queryEmployeeById() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入要查询的员工编号：");
        String id = scanner.nextLine();
        for (Employee employee : employees) {
            if (employee.getId().equals(id)) {
                System.out.println(employee);
                return;
            }
        }
        System.out.println("员工编号不存在，查询失败！");
    }

    private static void queryAllEmployees() {
        for (Employee employee : employees) {
            System.out.println(employee);
        }
    }
}

class Employee {
    private String id;
    private String name;
    private String gender;
    private int age;
    private String department;

    public Employee(String id, String name, String gender, int age, String department) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.age = age;
        this.department = department;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getDepartment() {
        return department;
    }

    public void setDepartment(String department) {
        this.department = department;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                ", department='" + department + '\'' +
                '}';
    }
}

在这个实现中，我们使用了一个 `ArrayList` 来存储所有的员工信息，并通过一个 `switch` 语句实现了不同功能的选择。在添加、删除、修改和查询员工信息时，我们通过 `Scanner` 类来获取用户输入的信息，并对员工信息进行相应的操作。同时，我们还定义了一个 `Employee` 类来表示每个员工的基本信息，方便后续的操作。