Which @NotNull Annotation Should Java Developers Use?

What @NotNull Java Annotation Should You Use?

Understanding the Issue

Many Java developers seek to improve their code readability and leverage tooling to prevent NullPointerExceptions. However, the multitude of available @NotNull annotations can be confusing and incompatible, leading to the question: which annotation is the most suitable for your needs?

Comparing Available Annotations

There are several @NotNull annotations available, each with its own purpose and compatibility. These include:

• javax.validation.constraints.NotNull (for runtime validation)
• edu.umd.cs.findbugs.annotations.NonNull (used by FindBugs/SpotBugs)
• javax.annotation.Nonnull (inactive JSR-305 annotation)
• org.jetbrains.annotations.NotNull (used by IntelliJ IDEA)
• lombok.NonNull (for Project Lombok)
• androidx.annotation.NonNull (available in Android)
• org.eclipse.jdt.annotation.NonNull (used by Eclipse)

Pragmatic Solution

Some debate exists around the ideal @NotNull annotation due to the dormancy of JSR 305. However, in practice, choosing the most appropriate annotation depends on your specific tooling and preferences.

Syntax Recommendations

For readability and platform independence, it's preferable to avoid IDE-specific or framework-dependent annotations like org.jetbrains.annotations.

javax.annotation: A Balanced Approach

Based on syntax and support, javax.annotation is a reasonable choice. It's shorter than javax.validation.constraints and doesn't introduce additional dependencies like JEE.

Implementation Variability

While many @NotNull annotations have similar syntax, their implementations differ.

• Runtime vs. Compile Time: javax.annotation, javax.validation.constraints, and org.checkerframework.checker.nullness.qual are runtime annotations, while others are compile-time annotations.
• Usage Context: Some annotations support only specific code contexts (e.g., fields, methods, parameters) while others have broader support.

Conclusion

Choosing the appropriate @NotNull Java annotation involves considering factors like syntax, implementation, and compatibility with your tooling. By understanding the options available and their distinctions, you can select the annotation that best meets your needs. It's important to note that a definitive "best" annotation may not exist, and a pragmatic approach that aligns with your specific usage context is recommended.

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