Which @NotNull Java annotation should I use?

Question

I\'m looking to make my code more readable as well as use tooling like IDE code inspection and/or static code analysis (FindBugs and Sonar) to avoid NullPointerExceptions.

Answer 1

If you are working on a big project, you may be better of creating your own @Nullable and/or @NotNull annotations.

For example:

@java.lang.annotation.Documented
@java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.CLASS)
@java.lang.annotation.Target({java.lang.annotation.ElementType.FIELD,
                              java.lang.annotation.ElementType.METHOD,    
                              java.lang.annotation.ElementType.PARAMETER,
                              java.lang.annotation.ElementType.LOCAL_VARIABLE})
public @interface Nullable 
{
}

If you use the correct retention policy, then the annotations won't be available at runtime. From that point of view, it is just an internal thing.

Even though this is not a strict science, I think it makes most sense to use an internal class for it.

• It is an internal thing. (no functional or technical impact)
• With many many many usages.
• IDE's like IntelliJ support custom @Nullable/@NotNull annotations.
• Most frameworks prefer to use their own internal version as well.

Additional Questions (see comments):

How to configure this in IntelliJ ?

Click the "police officer" in the lower right corner of the IntelliJ status bar. And click "Configure inspections" in the popup. Next ...