利用Java Swing和MySQL实现1. 实现页面菜单，菜单项包括按名字读取、按学号读取、按班级读取； 2. 实现搜索框，用于输入名字或学号，根据名字或学号查询学生信息； 3. 实现班级下拉列表，用于选择班级并按班级查询学生信息。 4. 实现学生信息展示功能，展示从数据库中查询到的学生信息；的代码

以下是一个基于Java Swing和MySQL的学生信息管理系统的代码实现，包括菜单项、搜索框、班级下拉列表和学生信息展示功能的实现。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Vector;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;

public class StudentInfoManagementSystem extends JFrame implements ActionListener {

    // 数据库连接信息
    private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DB_URL = "jdbc:mysql://localhost:3306/student_info";
    private static final String USER = "root";
    private static final String PASSWORD = "root";

    // 界面元素
    private JTable table;
    private DefaultTableModel tableModel;
    private JTextField searchTextField;
    private JComboBox<String> classComboBox;
    private JButton searchButton;

    public StudentInfoManagementSystem() {
        // 设置窗口属性
        setTitle("学生信息管理系统");
        setSize(800, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // 创建菜单栏
        JPanel menuPanel = new JPanel();
        JLabel nameLabel = new JLabel("姓名：");
        searchTextField = new JTextField();
        searchTextField.setPreferredSize(new Dimension(100, 25));
        searchButton = new JButton("查询");
        searchButton.addActionListener(this);
        JLabel classLabel = new JLabel("班级：");
        classComboBox = new JComboBox<String>(getClasses());
        classComboBox.addActionListener(this);
        menuPanel.add(nameLabel);
        menuPanel.add(searchTextField);
        menuPanel.add(searchButton);
        menuPanel.add(classLabel);
        menuPanel.add(classComboBox);
        getContentPane().add(menuPanel, BorderLayout.NORTH);

        // 创建学生信息展示区域
        tableModel = new DefaultTableModel();
        table = new JTable(tableModel);
        JScrollPane tableScroll = new JScrollPane(table);
        getContentPane().add(tableScroll, BorderLayout.CENTER);
    }

    // 获取班级列表
    private String[] getClasses() {
        String[] classes = null;
        Connection conn = null;
        try {
            // 数据库连接
            Class.forName(JDBC_DRIVER);
            conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);

            // 查询班级列表
            String sql = "SELECT DISTINCT class FROM student";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            ResultSet rs = pstmt.executeQuery();
            Vector<String> classList = new Vector<String>();
            while (rs.next()) {
                classList.add(rs.getString("class"));
            }

            // 转换为数组
            classes = new String[classList.size()];
            for (int i = 0; i < classList.size(); i++) {
                classes[i] = classList.get(i);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                // 关闭数据库连接
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return classes;
    }

    // 查询学生信息
    private void queryStudentInfo(String nameOrId, String className) {
        Connection conn = null;
        try {
            // 数据库连接
            Class.forName(JDBC_DRIVER);
            conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);

            // 查询学生信息
            String sql = "SELECT * FROM student WHERE name LIKE ? OR id LIKE ? OR class = ?";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, "%" + nameOrId + "%");
            pstmt.setString(2, "%" + nameOrId + "%");
            pstmt.setString(3, className);
            ResultSet rs = pstmt.executeQuery();

            // 显示查询结果
            tableModel.setRowCount(0);
            while (rs.next()) {
                Vector<Object> rowData = new Vector<Object>();
                rowData.add(rs.getString("id"));
                rowData.add(rs.getString("name"));
                rowData.add(rs.getInt("age"));
                rowData.add(rs.getString("gender"));
                rowData.add(rs.getString("class"));
                tableModel.addRow(rowData);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                // 关闭数据库连接
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == searchButton) {
            // 查询学生信息
            String nameOrId = searchTextField.getText();
            String className = (String) classComboBox.getSelectedItem();
            queryStudentInfo(nameOrId, className);
        } else if (e.getSource() == classComboBox) {
            // 根据班级查询学生信息
            String className = (String) classComboBox.getSelectedItem();
            queryStudentInfo("", className);
        }
    }

    public static void main(String[] args) {
        StudentInfoManagementSystem frame = new StudentInfoManagementSystem();
        frame.setVisible(true);
    }
}

上述代码实现了一个简单的学生信息管理系统，包括菜单项、搜索框、班级下拉列表和学生信息展示功能。需要注意的是，代码中省略了异常处理等细节处理，仅供参考。