学生开始考试页面 public static void studentStartExam 从数据库读取题目并逐题显示给学生答题 学生答题完成后计算得分并保存到数据库 连接数据库做完一题可以选择下一题或则完成将代码给出

import java.sql.*;

public class StudentExamPage { private static final String DB_URL = "jdbc:mysql://localhost/exam"; private static final String DB_USER = "root"; private static final String DB_PASSWORD = "123456";

public static void studentStartExam() {
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;
    try {
        // 连接数据库
        conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
        stmt = conn.createStatement();

        // 从数据库读取题目
        String sql = "SELECT * FROM questions";
        rs = stmt.executeQuery(sql);

        // 逐题显示给学生答题
        while (rs.next()) {
            int questionId = rs.getInt("id");
            String questionContent = rs.getString("content");
            String optionA = rs.getString("option_a");
            String optionB = rs.getString("option_b");
            String optionC = rs.getString("option_c");
            String optionD = rs.getString("option_d");

            System.out.println("Question " + questionId + ": " + questionContent);
            System.out.println("A. " + optionA);
            System.out.println("B. " + optionB);
            System.out.println("C. " + optionC);
            System.out.println("D. " + optionD);

            // 学生答题
            System.out.print("Your answer: ");
            String studentAnswer = System.console().readLine();

            // 保存学生答案到数据库
            sql = "INSERT INTO student_answers (question_id, student_answer) VALUES (?, ?)";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, questionId);
            pstmt.setString(2, studentAnswer);
            pstmt.executeUpdate();
        }

        // 计算得分
        sql = "SELECT COUNT(*) AS correct_count FROM questions q JOIN student_answers a ON q.id = a.question_id WHERE q.answer = a.student_answer";
        rs = stmt.executeQuery(sql);
        rs.next();
        int correctCount = rs.getInt("correct_count");
        int totalScore = correctCount * 10;

        // 保存得分到数据库
        sql = "INSERT INTO student_scores (score) VALUES (?)";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, totalScore);
        pstmt.executeUpdate();

        System.out.println("Your score is " + totalScore);
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭连接
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}