Why sometimes I get data and sometimes not, although I don’t change the code?

Question

Java

I want to get weather data from this page: https://www.google.com/search?client=opera&q=weather...

public class Parser2 {

    public static void main(String[] args) throws IOException {
        Parser2 parser = new Parser2();
        System.out.println(parser.valueList());
        System.out.println(parser.allPrintConsole());
    }

    static Elements getPage() throws IOException // возвращает всю таблицу с погодой
    {
        String url = "https://www.google.com/search?client=opera&q=погода+довск&sourceid=opera&ie=UTF-8&oe=UTF-8";
        Document page = Jsoup.connect(url).get();
        Elements tableWth =page.select("div[class=nawv0d vk_c]"); // вся таблица с погодой

        return tableWth;
    }

    public ArrayList<String> allPrintConsole() throws IOException
    {
        Elements tableWth = getPage();

        String weekData = tableWth.select("div[class=wob_dts vk_gy vk_sh]").text(); // ячейка дата с временем
        String temp = tableWth.select("span[class=wob_t TVtOme]").text(); //кол-во градусов, можно будет взять для: от до
        String whater = tableWth.select("span[id=wob_hm]").text();
        String weter = tableWth.select("span[id=wob_ws]").text();

        ArrayList<String> print = new ArrayList<>(); //тут храняться данные
        print.add(weekData);
        print.add(temp+"°С");
        print.add(whater);
        print.add(weter);

        return print;

    }

    public static   ArrayList<String> weekList() throws IOException {

        Elements peek = getPage().select("div[class=wob_dfc]");

        String[] weekName = peek.select("div[class=QrNVmd Z1VzSb]").text().split(" "); // дни недели

        ArrayList<String> week = new ArrayList<>();

        for (int i = 0; i < weekName.length; i++) {
            week.add(weekName[i]); // week.size() = 8
        }
        return week;
    }

    public ArrayList<String> valueList() throws IOException {

        Elements peek = getPage().select("div[class=wob_dfc]");

        ArrayList<String> list = new ArrayList<>();

        for (int i = 0; i < 32; i+=2) {
            String first = peek.select("span[class=wob_t]").get(i).text();
            list.add(first); //list.size() = 16
        }
        return list;
    }
}

Sometimes the data is displayed, and sometimes not, the code is not changed

Answer 1

Good afternoon!
The first thing I will say is that it is not a good idea to use a parser (Jsoup or whatever) to get the weather forecast.
Use the API services provided for this. For example, OpenWeatherMap
Next is the answer to your question:

Why sometimes I get data and sometimes not, although I don’t change the code?

You may not change the code you wrote, but the page (DOM) of the site itself may change due to which you are seeing an error