CODEWITHSUNDEEP
javaintellij-ideaannotationsjetbrains-ide
ycomp
ycomp

Reputation: 8583

IntelliJ null check warnings

I often have code like this:

protected @Nullable Value value;

public boolean hasValue() { return value != null; }

the problem with this is that when I do null checks like so:

if (!hasValue()) throw...
return value.toString();

then IntelliJ will warn me about a possible NPE

whereas

if (value != null) throw...
return value.toString();

avoids this warning.

is there a way to decorate my hasValue() method so that IntelliJ knows it does a null check? and won't display the warning?

Upvotes: 11

Views: 5069

Answers (2)

Christian Kern
Christian Kern

Reputation: 62

The actual correct answer is to add a @Contract annotation to the method checking for null.

See: https://blog.jetbrains.com/idea/2013/10/better-control-flow-analysis-with-contract-annotations-and-intellij-idea-13/

Credits: How can I make IntelliJ IDEA understand my null-checking method?

Upvotes: 2

Andremoniy
Andremoniy

Reputation: 34920

Intellij-Jetbrains is very clever IDE and itself suggests you way for solving many problems.

Look at screenshot below. It suggests your five ways for removing this warning:

1) add assert value != null;

2) replace return statement with return value != null ? value.toString() : null;

3) surround with 

    if (value != null) {
        return value.toString();
    }

4) suppress inspection for this particular statement by adding commentary:

//noinspection ConstantConditions
return value.toString();

5) add at least, as earlier @ochi suggested use @SuppressWarnings("ConstantConditions") annotation which can be used for method or for whole class.

To invoke this context menu use shortcut keys Alt+Enter (I think they are common for all OS).

enter image description here

Upvotes: 6

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