在循环中使用Jsoup connect().第一个请求总是比其他所有请求慢得多

我正在创建一个小应用程序,用于衡量HTML文档加载所需的时间,每隔x秒检查一次.

我在循环中使用jsoup:

    Connection.Response response = null;

    for (int i = 0; i < totalGets; i++) {
        long startTime = System.currentTimeMillis();

        try {
            response = Jsoup.connect(url)
                    .userAgent(USER_AGENT)  //just using a Firefox user-agent
                    .timeout(30_000)
                    .execute();
        } catch (IOException e) {
            if (e.getMessage().contains("connect timed out")) {
                System.out.println("Request timed out after 30 seconds!");
            }
        }

        long currentTime = System.currentTimeMillis();

        System.out.println("Response time: " + (currentTime - startTime) + "ms" + "\tResponse code: " + response.statusCode());

        sleep(2000);
    }

我遇到的问题是,无论什么网站,jsoup连接的第一次执行总是慢于后续的一次.

这是我的输出 https://www.google.com

Response time: 934ms    Response code: 200
Response time: 149ms    Response code: 200
Response time: 122ms    Response code: 200
Response time: 136ms    Response code: 200
Response time: 128ms    Response code: 200

这就是我的成就 http://stackoverflow.com

Response time: 440ms    Response code: 200
Response time: 182ms    Response code: 200
Response time: 187ms    Response code: 200
Response time: 193ms    Response code: 200
Response time: 185ms    Response code: 200

为什么第一次连接后它总是更快？有没有更好的方法来确定文档的加载速度？