Java. Which @Nullable should I use to mark return value with one?

Question

My java method can return null and non null results. I want mark method with @Nullable annotation to make it more readable.

I used com.sun.istack.internal.Nullable but sonar says Classes from "sun.*" packages should not be used. Code smell Major squid:S1191.

I try to find more similar annotations, but there are variants from different IDE, not from java vendor.

Does java (oracle) provides alternatives for nullable annotation or I should use third party libraries only? If I have to use third party library to have an @Nullable which one should be good?

Use `javax.annotation.Nullable` from [JSR 305](https://jcp.org/en/jsr/detail?id=305) instead of an internal Sun class. You can find that annotation in for example [com.google.code.findbugs:jsr305](http://search.maven.org/#artifactdetails%7Ccom.google.code.findbugs%7Cjsr305%7C3.0.2%7Cjar) — Jesper, Jul 25 '17 at 09:25
Relevant/Duplicate : [Can't find @Nullable inside javax.annotation.*](https://stackoverflow.com/questions/19030954/cant-find-nullable-inside-javax-annotation) — Aaron, Jul 25 '17 at 09:25
i promote the comment from @dehasi. just return an optional, this is probably the most readable version — Lino, Jul 25 '17 at 09:27
@dehasi Like it. but the method is private, and it is called from lambda, the result is wrapped with optional — Sergii, Jul 25 '17 at 09:38
Related: https://stackoverflow.com/questions/4963300/which-notnull-java-annotation-should-i-use — tkruse, Dec 06 '18 at 01:23

score 5 · Accepted Answer · answered Jul 25 '17 at 09:37

Well, I think for Sonar you could use edu.umd.cs.findbugs.annotations.*, which are deprecated and advise you to use javax.annotation.Nullable.

I mainly use the Jetbrains ones, https://www.jetbrains.com/help/idea/nullable-and-notnull-annotations.html, but my main goal is the analysis in IntelliJ.

Grzegorz Piwowarek · Answer 2 · 2022-07-18T15:12:50.767

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If you can, consider using Optional<T> as the return type to make it more readable. You can express optionality utilizing the type system and benefit from the rich monadic-like API instead of wondering which annotation is the right one.

edited Jul 18 '22 at 15:12

answered Jul 25 '17 at 10:39

Grzegorz Piwowarek

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score 0 · Answer 3 · answered Oct 07 '17 at 16:58

Optional<T> or @Nullable or @return tag from java-doc are ways to say to users of your API that a method can return null. But you mentioned in comments that your method is private. It means that nobody, except you, can use it. That's why no additional stuff needed.

score 0 · Answer 4 · answered Dec 06 '18 at 01:25

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With FIndbugs/Spotbugs, use @CheckForNull. See https://sourceforge.net/p/findbugs/bugs/1181)

answered Dec 06 '18 at 01:25

tkruse

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Java. Which @Nullable should I use to mark return value with one?

4 Answers4