java SonarQube 阻止程序问题 NullPointerException 可能会被抛出，因为这里的“联系人”可以为空
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/40233277/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
SonarQube Blocker Issue NullPointerException might be thrown as 'contacts' is nullable here
提问by BeginnersSake
I have a method that returns list of contacts. When I am running this code on SonarQube server. It shows a blocker issue stating NullPointerException might be thrown as 'contacts' is nullable here.. How to resolve this?
我有一个返回联系人列表的方法。当我在 SonarQube 服务器上运行此代码时。它显示了一个阻止程序问题，指出NullPointerException 可能会被抛出，因为“联系人”在这里可以为空。. 如何解决这个问题？
List<Contact> getContactDetails(){...}
public void checkSize() {
List<Contact> contacts = getContactDetails();
syso(contacts.size());
}
回答by Gernot R. Bauer
Depending on your implementation of getContactDetails(), this method might return null, and so the line
根据您的 实现getContactDetails()，此方法可能会返回null，因此该行
syso(contacts.size());
might fail due to an NPE because contactscould be null.
可能由于 NPE 而失败，因为contacts可能是null.
Fix this by either adding
通过添加来解决此问题
if(contacts != null) {
syso(contacts.size());
} else {
// exception, error handling or nothing
}
or by not returning nullin getContactDetails().
或者通过不返回null在getContactDetails()。
回答by walen
Sonar is complaining that you're calling .size()on something that might be null. So make sure you don't do that:
声纳抱怨您正在调用.size()可能是null. 因此，请确保您不要这样做：
List<Contact> getContactDetails(){...}
public void checkSize() {
List<Contact> contacts = getContactDetails();
syso(contacts == null ? "contacts is null" : contacts.size());
}
