使用查询完成后，正确关闭连接

Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;

try {
    // 创建数据库连接
    connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");

    // 创建Statement对象
    statement = connection.createStatement();

    // 执行查询语句
    resultSet = statement.executeQuery("SELECT * FROM mytable");

    // 处理查询结果
    while (resultSet.next()) {
        // 处理每一行数据
    }

} catch (SQLException e) {
    // 处理异常
} finally {
    // 关闭ResultSet对象
    if (resultSet != null) {
        try {
            resultSet.close();
        } catch (SQLException e) {
            // 处理异常
        }
    }

    // 关闭Statement对象
    if (statement != null) {
        try {
            statement.close();
        } catch (SQLException e) {
            // 处理异常
        }
    }

    // 关闭Connection对象
    if (connection != null) {
        try {
            connection.close();
        } catch (SQLException e) {
            // 处理异常
        }
    }
}