Report False Positive NullPointer

[kfersch]

Sonaqube Version: * Version 8.9.9 (build 56886)
Rule: Null pointers should not be dereferenced - “getName()” can return null

Codesample:

class Playground {
    public static void main(String[ ] args) {
        Response response = null;

        if(response != null && response.getName() != null && response.getName().equals("")) {
           if(response.getName().equals("a")) {
             System.out.println("This is also a false-positive I also get an Error for that, but clearly it is checked before");
           }
            System.out.println("Hello world");
        }else {
            System.out.println("No NullPointer even it is null");
        }
    }
}

class Response {
    String name;
    String result;

    public String getName(){return name;}

    public String getResult(){return result;}
}

Expected Solution:
The Rule is not triggered when before a NullCheck was made at the IF clause.

[Quentin (Quentin Jaquier)]

Hello @kfersch and welcome to the Sonar Community.

I invite you to have a look at this post, answering to a similar issue:

[False Positive]A "NullPointerException" could be thrown;

Hello @Bhuvana The analyzer assumes that two consecutive method calls do not necessarily return the same value. It means that a null check on the first call to getBody() is not enough to avoid a NPE. You should extract the method call into a variable to not have an issue. In a way, this is a limitation of the analyzer, it is not able to detect if a method always returns the same value or not, so it reports an issue anyway, taking the risk to report false positives. If you are confident your c…

I hope it clarifies the situation.

Best,
Quentin

[kfersch]

But what is about the second - False Positive ? Here the same even in a new if ?

if(response != null && response.getName() != null ) {
           if(response.getName().equals("a")) {
             System.out.println("This is also a false-positive I also get an Error for that, but clearly it is checked before");
           } 
        }

[Quentin (Quentin Jaquier)]

The situation is the same in this second example: if getName() returns null on the second call, you will have a NPE.
As mentioned in the other post, either you accept the code as it is, or change it to something like:

if(response != null) {
           String name = response.getName();
           if(name != null && name.equals("a")) {
           } 
}