如何使用从数据库中检索的值来创建HashMap？

import java.sql.*;
import java.util.HashMap;

public class DatabaseToHashMapExample {
    public static void main(String[] args) {
        // 数据库连接信息
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";

        // 创建HashMap
        HashMap<String, String> hashMap = new HashMap<>();

        try {
            // 连接数据库
            Connection connection = DriverManager.getConnection(url, username, password);

            // 执行查询
            String query = "SELECT key_column, value_column FROM mytable";
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(query);

            // 遍历结果集并创建HashMap
            while (resultSet.next()) {
                String key = resultSet.getString("key_column");
                String value = resultSet.getString("value_column");
                hashMap.put(key, value);
            }

            // 关闭数据库连接
            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        // 打印HashMap
        System.out.println(hashMap);
    }
}