Question

我目前正在编写一个Java程序，该程序从html获取源代码并对其进行解析以获取值。正常工作正常，但是一旦我尝试让它在while循环中运行并每30秒重新获取数据，我的PC速度就会变慢，直到我手动停止程序为止。

while(true) {                           
    try { 
                                URL url = new URL("https://www.reddit.com/r/gaming/");
                                URLConnection urlConn = url.openConnection();

                                System.out.println(urlConn.getContentType());  //it returns text/html

                                BufferedReader in = new BufferedReader
                                (new InputStreamReader(urlConn.getInputStream()));

                                File test = new File("test");
                                BufferedWriter writer = new BufferedWriter(new FileWriter(test));

                                String text;

                                while ((text = in.readLine()) != null) {

                                    writer.write (text);
                                }

                                writer.close();
                                in.close();

                                String content = new String(Files.readAllBytes(Paths.get("test")), "UTF-8");

                                Pattern pattern = Pattern.compile("title=(.*?)\">");
                                Matcher matcher = pattern.matcher(content);
                                if (matcher.find()) {
                                    System.out.println(matcher.group(1));
                                    if (Integer.valueOf((matcher.group(1))) <= 99999999) {
                                        Clip clip = AudioSystem.getClip();
                                        AudioInputStream inputStream = AudioSystem.getAudioInputStream(new File("alert.wav"));
                                        clip.open(inputStream);
                                        clip.start(); 
                                    }
                                }
        Thread.sleep(30000);

    } catch (MalformedURLException f) {
        f.printStackTrace();
    } catch (IOException f) {
        f.printStackTrace();
    } catch (InterruptedException f) {
        f.printStackTrace();
    } catch (UnsupportedAudioFileException e) {
        e.printStackTrace();
    } catch (LineUnavailableException e) {
        e.printStackTrace();
    }
}

任何提示为何会发生这种情况？

Answer 1

也许我对代码有误解，但是我认为Thread.sleep()仅在您不抛出时才运行。我认为您想将其放在try / catch之外，这样，如果失败，则等待30秒再尝试。否则，如果某个原因导致throw，您将立即重试，由于自上次尝试以来什么都没有真正改变，因此您将一遍又一遍地立即throw。

现在，您的代码是：

while (true) {
    try {
        // Do a lot of things that can throw
        if(something_bad_happens) throw new Error();

        /*
         * This sleep will only be reached
         * if we don't throw
         */
        Thread.sleep(30000);
    } catch (errors) {
        // Deal with errors
    }
}

我认为您实际上想要这个：

while (true) {
    try {
        // Do a lot of things that can throw
        if(something_bad_happens) throw new Error();
    } catch (errors) {
        // Deal with errors
    }

    // Always sleep between attempts no matter what
    Thread.sleep(30000);
}

循环+睡眠会使PC变慢

1 个答案: