无法将数据库数据填充到jcombobox中

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.JComboBox;

public class DatabaseComboBox {
    public static void main(String[] args) {
        // 建立数据库连接
        Connection connection = null;
        try {
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");
            
            // 执行查询语句
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery("SELECT * FROM mytable");
            
            // 填充数据到JComboBox
            JComboBox<String> comboBox = new JComboBox<>();
            while (resultSet.next()) {
                String data = resultSet.getString("column_name");
                comboBox.addItem(data);
            }
            
            // 使用填充好的JComboBox
            // ...
            
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭数据库连接
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}