用java+mysql写一个小型学生成绩管理系统 用控制台输入

好的，这是一个比较简单的学生成绩管理系统，主要包括学生信息管理和成绩管理两个功能。以下是代码实现：

import java.sql.*;

public class StudentGradeManagementSystem {
    // 数据库连接信息
    private static final String url = "jdbc:mysql://localhost:3306/student";
    private static final String username = "root";
    private static final String password = "123456";

    // 数据库连接对象
    private Connection conn = null;
    // SQL执行对象
    private Statement stmt = null;
    // 结果集对象
    private ResultSet rs = null;

    // 构造方法，连接数据库
    public StudentGradeManagementSystem() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url, username, password);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }

    // 查询学生信息
    public void queryStudent() {
        try {
            stmt = conn.createStatement();
            rs = stmt.executeQuery("SELECT * FROM student");
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                String gender = rs.getString("gender");
                int age = rs.getInt("age");
                System.out.println(id + "\t" + name + "\t" + gender + "\t" + age);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 添加学生信息
    public void addStudent(String name, String gender, int age) {
        try {
            stmt = conn.createStatement();
            String sql = "INSERT INTO student(name, gender, age) VALUES('" + name + "', '" + gender + "', " + age + ")";
            int count = stmt.executeUpdate(sql);
            if (count > 0) {
                System.out.println("添加成功！");
            } else {
                System.out.println("添加失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 修改学生信息
    public void updateStudent(int id, String name, String gender, int age) {
        try {
            stmt = conn.createStatement();
            String sql = "UPDATE student SET name='" + name + "', gender='" + gender + "', age=" + age + " WHERE id=" + id;
            int count = stmt.executeUpdate(sql);
            if (count > 0) {
                System.out.println("修改成功！");
            } else {
                System.out.println("修改失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 删除学生信息
    public void deleteStudent(int id) {
        try {
            stmt = conn.createStatement();
            String sql = "DELETE FROM student WHERE id=" + id;
            int count = stmt.executeUpdate(sql);
            if (count > 0) {
                System.out.println("删除成功！");
            } else {
                System.out.println("删除失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 查询学生成绩
    public void queryGrade(int id) {
        try {
            stmt = conn.createStatement();
            rs = stmt.executeQuery("SELECT * FROM grade WHERE student_id=" + id);
            while (rs.next()) {
                int gradeId = rs.getInt("id");
                int studentId = rs.getInt("student_id");
                int grade = rs.getInt("grade");
                String subject = rs.getString("subject");
                System.out.println(gradeId + "\t" + studentId + "\t" + subject + "\t" + grade);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 添加学生成绩
    public void addGrade(int id, String subject, int grade) {
        try {
            stmt = conn.createStatement();
            String sql = "INSERT INTO grade(student_id, subject, grade) VALUES(" + id + ", '" + subject + "', " + grade + ")";
            int count = stmt.executeUpdate(sql);
            if (count > 0) {
                System.out.println("添加成功！");
            } else {
                System.out.println("添加失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 修改学生成绩
    public void updateGrade(int gradeId, int grade) {
        try {
            stmt = conn.createStatement();
            String sql = "UPDATE grade SET grade=" + grade + " WHERE id=" + gradeId;
            int count = stmt.executeUpdate(sql);
            if (count > 0) {
                System.out.println("修改成功！");
            } else {
                System.out.println("修改失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 删除学生成绩
    public void deleteGrade(int gradeId) {
        try {
            stmt = conn.createStatement();
            String sql = "DELETE FROM grade WHERE id=" + gradeId;
            int count = stmt.executeUpdate(sql);
            if (count > 0) {
                System.out.println("删除成功！");
            } else {
                System.out.println("删除失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 关闭数据库连接
    private void close() {
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        StudentGradeManagementSystem system = new StudentGradeManagementSystem();
        int choice = 0;
        do {
            System.out.println("请选择操作：");
            System.out.println("1.查询学生信息");
            System.out.println("2.添加学生信息");
            System.out.println("3.修改学生信息");
            System.out.println("4.删除学生信息");
            System.out.println("5.查询学生成绩");
            System.out.println("6.添加学生成绩");
            System.out.println("7.修改学生成绩");
            System.out.println("8.删除学生成绩");
            System.out.println("9.退出");
            System.out.print("请选择：");
            choice = Integer.parseInt(System.console().readLine());
            switch (choice) {
                case 1:
                    system.queryStudent();
                    break;
                case 2:
                    System.out.print("请输入学生姓名：");
                    String name = System.console().readLine();
                    System.out.print("请输入学生性别：");
                    String gender = System.console().readLine();
                    System.out.print("请输入学生年龄：");
                    int age = Integer.parseInt(System.console().readLine());
                    system.addStudent(name, gender, age);
                    break;
                case 3:
                    System.out.print("请输入要修改的学生ID：");
                    int id = Integer.parseInt(System.console().readLine());
                    System.out.print("请输入学生姓名：");
                    name = System.console().readLine();
                    System.out.print("请输入学生性别：");
                    gender = System.console().readLine();
                    System.out.print("请输入学生年龄：");
                    age = Integer.parseInt(System.console().readLine());
                    system.updateStudent(id, name, gender, age);
                    break;
                case 4:
                    System.out.print("请输入要删除的学生ID：");
                    id = Integer.parseInt(System.console().readLine());
                    system.deleteStudent(id);
                    break;
                case 5:
                    System.out.print("请输入要查询成绩的学生ID：");
                    id = Integer.parseInt(System.console().readLine());
                    system.queryGrade(id);
                    break;
                case 6:
                    System.out.print("请输入学生ID：");
                    id = Integer.parseInt(System.console().readLine());
                    System.out.print("请输入科目：");
                    String subject = System.console().readLine();
                    System.out.print("请输入成绩：");
                    int grade = Integer.parseInt(System.console().readLine());
                    system.addGrade(id, subject, grade);
                    break;
                case 7:
                    System.out.print("请输入要修改的成绩ID：");
                    int gradeId = Integer.parseInt(System.console().readLine());
                    System.out.print("请输入成绩：");
                    grade = Integer.parseInt(System.console().readLine());
                    system.updateGrade(gradeId, grade);
                    break;
                case 8:
                    System.out.print("请输入要删除的成绩ID：");
                    gradeId = Integer.parseInt(System.console().readLine());
                    system.deleteGrade(gradeId);
                    break;
                case 9:
                    System.out.println("谢谢使用！");
                    break;
                default:
                    System.out.println("选择有误，请重新输入！");
                    break;
            }
        } while (choice != 9);
    }
}

注意，这里使用的是 JDBC 连接数据库，需要先在本地安装 MySQL 并创建名为 student 的数据库，其中包含两个表 student 和 grade，具体表结构如下：

CREATE TABLE `student` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  `gender` varchar(10) NOT NULL,
  `age` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4;

CREATE TABLE `grade` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) NOT NULL,
  `subject` varchar(20) NOT NULL,
  `grade` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_student_id` (`student_id`),
  CONSTRAINT `fk_student_id` FOREIGN KEY (`student_id`) REFERENCES `student` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8mb4;

此外，为了可以在控制台输入，代码中使用了 System.console().readLine() 方法，如果是在 IDE 中运行需要改为 Scanner 的方式读取输入。