空指针异常检查

发布于 2025-01-04 19:05:14 字数 668 浏览 4 评论 0原文

我有一个类文件，当我编译时，该文件始终在特定行中显示空指针异常。我按如下方式处理空检查。

108    doc = Jsoup.parse(html, brandUrl);

109    Element div = doc.getElementById("eventTTL");
110    String attr = div.attr("eventTTL");
111    Date closingDate = new Date(Long.parseLong(attr));
112    Elements mainForm = doc.select("div#main-form");
113    Elements mainDivs = mainForm.select("DIV");

java.lang.NullPointerException 在 com.textT.at.Chickyur.main(Chickyur.java:110)

if(div != null)
String attr = div.attr("eventTTL"); 

 Also tried 
 if(div.attr("eventTTL") != null)
 String attr = div.attr("eventTTL");

我仍然不断收到异常。怎么了？有什么想法吗？

原文

I have a class file which when i compile shows me Null pointer exception in a particular line all the time. I handled null check as below.

108    doc = Jsoup.parse(html, brandUrl);

109    Element div = doc.getElementById("eventTTL");
110    String attr = div.attr("eventTTL");
111    Date closingDate = new Date(Long.parseLong(attr));
112    Elements mainForm = doc.select("div#main-form");
113    Elements mainDivs = mainForm.select("DIV");

java.lang.NullPointerException
at com.textT.at.Chickyur.main(Chickyur.java:110)

if(div != null)
String attr = div.attr("eventTTL"); 

 Also tried 
 if(div.attr("eventTTL") != null)
 String attr = div.attr("eventTTL");

Still i keep getting the exceptions. What is wrong? any thoughts?

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初心 2025-01-11 19:05:14

我无法通过上面发布的代码准确地判断您的代码的结构，但这应该修复 NullPointerException：

Element div = doc.getElementById("eventTTL");
String attr = "";

if(div != null)
    attr = div.attr("eventTTL");

如果您在那之后继续收到异常，我猜问题出在代码的其他地方，并且你需要更新你的例子。

I can't tell by the code posted above exactly how your code is structured, but this should fix the NullPointerException:

Element div = doc.getElementById("eventTTL");
String attr = "";

if(div != null)
    attr = div.attr("eventTTL");

If you continue getting Exceptions after that, I would guess the issue is elsewhere in the code and you need to update your example.

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北斗星光 2025-01-11 19:05:14

您所做的代码更改将导致编译错误。不会创建任何类文件，因此您可能正在运行旧的损坏的类文件。

您可能想要这样做（扩展 if 的范围）。

doc = Jsoup.parse(html, brandUrl);

Element div = doc.getElementById("eventTTL");
if(div != null) {
    String attr = div.attr("eventTTL");
    Date closingDate = new Date(Long.parseLong(attr));
    Elements mainForm = doc.select("div#main-form");
    Elements mainDivs = mainForm.select("DIV");
    ...
}

The code change you made will result in a compile error. No class file will be created, so you are probably running the old broken class file.

You probably want do do this (extend the scope of the if).

doc = Jsoup.parse(html, brandUrl);

Element div = doc.getElementById("eventTTL");
if(div != null) {
    String attr = div.attr("eventTTL");
    Date closingDate = new Date(Long.parseLong(attr));
    Elements mainForm = doc.select("div#main-form");
    Elements mainDivs = mainForm.select("DIV");
    ...
}

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