从div中提取元素，jSoup返回null

Question

我正在尝试从网页中提取字符串：https://play.google.com/store/apps/details?id=com.bitmango.rolltheballunrollme。我想要的字符串是：<div class="id-app-title" tabindex="0">Roll the Ball™ - slide puzzle</div>。

我看了https://jsoup.org/cookbook/extracting-data/selector-syntax，我很确定我按照说明操作，但我得到了：

Exception in thread "main" java.lang.NullPointerException
at gaspacho.Gaspacho.getAppTitle(Gaspacho.java:109)
at gaspacho.Gaspacho.alphabetty(Gaspacho.java:94)
at gaspacho.Gaspacho.main(Gaspacho.java:27)
/home/david/.cache/netbeans/8.1/executor-snippets/run.xml:53: Java returned: 1
BUILD FAILED (total time: 3 seconds)

这是我正在使用的方法：

public void getAppTitle(String url){
    try {
        Document document = Jsoup.connect(url).get();

        Element appTitleElement = document.select("div.id-app-title" ).first();

        String title = appTitleElement.toString();

        System.out.println(title);

    } catch (IOException e) {
        e.printStackTrace();
    }
}

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