Which @NotNull Java annotation should I use?
For optimal compatibility, choose the javax.validation.constraints.NotNull annotation from JSR 380.
This annotation is the industry standard for verifying that your fields aren't null, recognised by an assortment of Java frameworks and tools.
Understanding compatibility issues
When Compatibility Matters
Choose the javax.validation.constraints.NotNull annotation for a versatile, virtually universal solution without any extra dependencies. Android developers can opt for the androidx.annotation.NonNull annotation that integrates smoothly with lint checks in Android Studio.
When using IDE-specific annotations
If you are using IntelliJ IDEA, then the org.jetbrains.annotations.NotNull annotation is a good choice, as it is designed to work synergistically with the IDE's strong analysis features. For Eclipse users, javax.validation.constraints.NotNull will suffice being supported natively.
When using framework-specific annotations
Framework specific annotations are also something to consider. For instance, Hibernate favours the javax.validation.constraints.NotNull as part of the default JSR 380 specification.
When using checker frameworks
The Checker Framework proposes its own annotations like org.checkerframework.checker.nullness.qual.NonNull, which serves the purpose of both compile-time and runtime checks. It also introduces NNEL (Non-Null Except Locals) which helps reducing verbosity in your code.
Future-proofing your choice
Checking for Standard updates
Stay updated with JSR-related news (305 and 308) as Java standards are always evolving. A new standardized @NotNull could be on the cards.
Making use of static analysis tools
Annotations like edu.umd.cs.findbugs.annotations.NonNull are beneficial for tools like FindBugs, helping early detection of potential bugs.
Updating your IDE
Always keep an eye out for updates in your IDE. As newer versions roll out, they can extend support for different annotations or introduce their own.
Making the right annotation choice
Enhancing readability
The chosen annotation should enhance code readability and avoid common mistakes. Near the top of the list of such mistakes is NullPointerException.
Using Stub strategy
Incorporating Checker Framework can be done without overhead by using stub files which will ensure that code remains reusable and does not get cluttered.
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