帮我写一个Java学生信息管理系统

好的，以下是一个简单的 Java 学生信息管理系统的实现。本系统使用 MySQL 数据库作为数据存储，使用 JDBC 连接数据库。实现的功能包括学生信息添加、查询、修改、删除等。

// Student.java

public class Student {
    private int id;
    private String name;
    private int age;
    private String gender;
    private String major;
    private String grade;

    // 构造方法
    public Student(int id, String name, int age, String gender, String major, String grade) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.major = major;
        this.grade = grade;
    }

    // getter 和 setter 方法
    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    public String getGender() {
        return gender;
    }

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

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }

    public String getGrade() {
        return grade;
    }

    public void setGrade(String grade) {
        this.grade = grade;
    }
}

// StudentDao.java

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDao {
    private Connection conn = null;

    // 构造方法，连接数据库
    public StudentDao() {
        String url = "jdbc:mysql://localhost:3306/student";
        String user = "root";
        String password = "123456";
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url, user, password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 添加学生信息
    public void addStudent(Student student) {
        String sql = "INSERT INTO student_info (id, name, age, gender, major, grade) VALUES (?, ?, ?, ?, ?, ?)";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, student.getId());
            ps.setString(2, student.getName());
            ps.setInt(3, student.getAge());
            ps.setString(4, student.getGender());
            ps.setString(5, student.getMajor());
            ps.setString(6, student.getGrade());
            ps.executeUpdate();
            ps.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 根据学生 ID 查询学生信息
    public Student getStudentById(int id) {
        Student student = null;
        String sql = "SELECT * FROM student_info WHERE id = ?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                student = new Student(rs.getInt("id"), rs.getString("name"), rs.getInt("age"),
                        rs.getString("gender"), rs.getString("major"), rs.getString("grade"));
            }
            rs.close();
            ps.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return student;
    }

    // 查询所有学生信息
    public List<Student> getAllStudents() {
        List<Student> students = new ArrayList<>();
        String sql = "SELECT * FROM student_info";
        try {
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery(sql);
            while (rs.next()) {
                Student student = new Student(rs.getInt("id"), rs.getString("name"), rs.getInt("age"),
                        rs.getString("gender"), rs.getString("major"), rs.getString("grade"));
                students.add(student);
            }
            rs.close();
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return students;
    }

    // 修改学生信息
    public void updateStudent(Student student) {
        String sql = "UPDATE student_info SET name = ?, age = ?, gender = ?, major = ?, grade = ? WHERE id = ?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, student.getName());
            ps.setInt(2, student.getAge());
            ps.setString(3, student.getGender());
            ps.setString(4, student.getMajor());
            ps.setString(5, student.getGrade());
            ps.setInt(6, student.getId());
            ps.executeUpdate();
            ps.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 删除学生信息
    public void deleteStudent(int id) {
        String sql = "DELETE FROM student_info WHERE id = ?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ps.executeUpdate();
            ps.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 关闭数据库连接
    public void close() {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

// StudentManagementSystem.java

import java.util.List;
import java.util.Scanner;

public class StudentManagementSystem {
    private StudentDao dao = new StudentDao();

    public void start() {
        Scanner scanner = new Scanner(System.in);
        boolean flag = true;
        while (flag) {
            System.out.println("学生信息管理系统");
            System.out.println("1. 添加学生信息");
            System.out.println("2. 查询学生信息");
            System.out.println("3. 修改学生信息");
            System.out.println("4. 删除学生信息");
            System.out.println("5. 退出系统");
            System.out.print("请选择操作：");
            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    addStudent(scanner);
                    break;
                case 2:
                    getStudent(scanner);
                    break;
                case 3:
                    updateStudent(scanner);
                    break;
                case 4:
                    deleteStudent(scanner);
                    break;
                case 5:
                    flag = false;
                    break;
                default:
                    System.out.println("输入错误，请重新选择");
                    break;
            }
        }
        scanner.close();
        dao.close();
        System.out.println("学生信息管理系统已退出");
    }

    // 添加学生信息
    private void addStudent(Scanner scanner) {
        System.out.print("请输入学生 ID：");
        int id = scanner.nextInt();
        System.out.print("请输入学生姓名：");
        String name = scanner.next();
        System.out.print("请输入学生年龄：");
        int age = scanner.nextInt();
        System.out.print("请输入学生性别：");
        String gender = scanner.next();
        System.out.print("请输入学生专业：");
        String major = scanner.next();
        System.out.print("请输入学生年级：");
        String grade = scanner.next();
        Student student = new Student(id, name, age, gender, major, grade);
        dao.addStudent(student);
        System.out.println("添加学生信息成功");
    }

    // 查询学生信息
    private void getStudent(Scanner scanner) {
        System.out.print("请输入要查询的学生 ID：");
        int id = scanner.nextInt();
        Student student = dao.getStudentById(id);
        if (student != null) {
            System.out.println("学生信息如下：");
            System.out.println("ID：" + student.getId());
            System.out.println("姓名：" + student.getName());
            System.out.println("年龄：" + student.getAge());
            System.out.println("性别：" + student.getGender());
            System.out.println("专业：" + student.getMajor());
            System.out.println("年级：" + student.getGrade());
        } else {
            System.out.println("未找到该学生信息");
        }
    }

    // 修改学生信息
    private void updateStudent(Scanner scanner) {
        System.out.print("请输入要修改的学生 ID：");
        int id = scanner.nextInt();
        Student student = dao.getStudentById(id);
        if (student != null) {
            System.out.println("原学生信息如下：");
            System.out.println("ID：" + student.getId());
            System.out.println("姓名：" + student.getName());
            System.out.println("年龄：" + student.getAge());
            System.out.println("性别：" + student.getGender());
            System.out.println("专业：" + student.getMajor());
            System.out.println("年级：" + student.getGrade());
            System.out.println("请输入新的学生信息：");
            System.out.print("姓名：");
            String name = scanner.next();
            System.out.print("年龄：");
            int age = scanner.nextInt();
            System.out.print("性别：");
            String gender = scanner.next();
            System.out.print("专业：");
            String major = scanner.next();
            System.out.print("年级：");
            String grade = scanner.next();
            student.setName(name);
            student.setAge(age);
            student.setGender(gender);
            student.setMajor(major);
            student.setGrade(grade);
            dao.updateStudent(student);
            System.out.println("修改学生信息成功");
        } else {
            System.out.println("未找到该学生信息");
        }
    }

    // 删除学生信息
    private void deleteStudent(Scanner scanner) {
        System.out.print("请输入要删除的学生 ID：");
        int id = scanner.nextInt();
        dao.deleteStudent(id);
        System.out.println("删除学生信息成功");
    }

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

注意：本程序只是一个简单的示例，实际应用中还需要加入更多的异常处理、输入校验、界面美化等功能。