@Target(value={METHOD,PARAMETER,FIELD}) @Retention(value=RUNTIME) @Documented @Nonnull(when=MAYBE) @TypeQualifierNickname public @interface Nullable
null under
 some circumstance.
 Leverages JSR-305 meta-annotations to indicate nullability in Java to common tools with JSR-305 support and used by Kotlin to infer nullability of Spring API.
Should be used at parameter, return value, and field level. Methods override should
 repeat parent @Nullable annotations unless they behave differently.
 
Can be used in association with @NonNullApi or @NonNullFields to
 override the default non-nullable semantic to nullable.
NonNullApi, 
NonNullFields, 
NonNull