为什么数据库中的所有数据都不显示在我的JTextfield上

import java.sql.*;

public class DatabaseExample {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        
        try {
            // 连接数据库
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://数据库地址:端口号/数据库名称";
            String username = "用户名";
            String password = "密码";
            conn = DriverManager.getConnection(url, username, password);
            
            // 执行查询
            stmt = conn.createStatement();
            String query = "SELECT * FROM 表名";
            rs = stmt.executeQuery(query);
            
            // 将数据填充到JTextField
            if (rs.next()) {
                String data = rs.getString("字段名");
                jTextField.setText(data);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stmt != null) {
                    stmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}