如何关闭dao java

try (Connection conn = DriverManager.getConnection(url, username, password);
     PreparedStatement stmt = conn.prepareStatement(sql)) {
    // 执行数据库操作
} catch (SQLException e) {
    // 异常处理
}

Connection conn = null;
try {
    conn = DriverManager.getConnection(url, username, password);
    // 执行数据库操作
} catch (SQLException e) {
    // 异常处理
} finally {
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            // 异常处理
        }
    }
}

DataSource dataSource = new BasicDataSource();
((BasicDataSource) dataSource).setUrl(url);
((BasicDataSource) dataSource).setUsername(username);
((BasicDataSource) dataSource).setPassword(password);

try (Connection conn = dataSource.getConnection();
     PreparedStatement stmt = conn.prepareStatement(sql)) {
    // 执行数据库操作
} catch (SQLException e) {
    // 异常处理
}