public @interface NonNull
@NonNull is a type annotation that indicates that a value is never null.
When applied to a member field's type, indicates that the field is never null after instantiation (construction) completes. When applied to a static field's type, indicates that the field is never null after the containing class is initialized.
This annotation is rarely written in source code, because it is the default.
No more than one of @NonNull and Nullable may be
written on a given type.
This annotation is associated with the NullnessChecker.
Nullable,
NullnessChecker