- Make sure that annotations.jar that can be found in the lib folder under the IntelliJ IDEA installation, is added to the module dependencies.
Tip
You can also use annotations from JSR-305 and FindBugs. In this case, make sure they are added to the classpath.
You can configure @Nullable and @NotNull annotations in the Inspections page of the Settings dialog (Constant conditions and exceptions - Configure annotations).
- Introduce the desired annotation before the package/class/field/variable/method/method parameter declaration.

