And related to the parent comment: Kotlin's compiler understands several kinds of @Nullable/@NotNull/@Nonnull annotations, and treats them as Kotlin's nullable/

And related to the parent comment: Kotlin's compiler understands several kinds of @Nullable/@NotNull/@Nonnull annotations, and treats them as Kotlin's nullable/not nullable ("@Nullable String" is treated as String?, for instance). In the other direction, Kotlin's nullable/not nullable is visible to the Java side as one of these sets of annotations (IntelliJ's IIRC), which allows for instance annotation processors like Dagger 2 to know when something can be null or not.