What is the meaning of Possible null pointer dereference in findbug?

Question

I am using Sonar and I have got this kind of violation from it for a peace of my code:

 Correctness - Possible null pointer dereference  

Has a

Answer 1

In simple language, if a variable value is assigned as null, and you try to access it with any inbuilt method like add/get. Then null pointer dereference issue comes with SONAR. Because there are changes for it go null, and throw null pointer exception. Try to avoid it if possible.

For example:

File file=null;
file.getName();

will throw "Possible null pointer dereference"

It may not happen directly as mentioned in the example, it can be unintentionally.