Getting rid of NP_NULL_ON_SOME_PATH_FROM_RETURN_VA

问题:

I'm getting NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE in this snippet

final Integer id = Ints.tryParse(idString);
FailReason.NO_SUCH_THING.checkCondition(id!=null);
something.setId(id.intValue());

Here, checkCondition works just like Preconditions.checkArgument except for it throws my own exception. Throwing NPE or IAE is not appropriate here, as it's checking an external input rather than a programming error.

FindBugs complains that "The return value from a method is dereferenced without a null check, and the return value of that method is one that should generally be checked for null. This may lead to a NullPointerException when the code is executed."

Can I teach FindBugs that checkCondition never returns normally when the argument is false?

回答1:

I (sort of) solved it by adding

assert id!=null;

It's redundant and ugly, but still less ugly than @SuppressFBWarnings and more local.

回答2:

Try using java.util.Objects.requireNonNull to please FindBugs:

final Integer id = Ints.tryParse(idString);
FailReason.NO_SUCH_THING.checkCondition(id!=null);
something.setId(Objects.requireNonNull(id).intValue());

Or you might be able to use java.util.Objects.isNull to fool FindBugs.

final Integer id = Ints.tryParse(idString);
FailReason.NO_SUCH_THING.checkCondition(!Objects.isNull(id));
something.setId(id.intValue());