I've got a

BehaviorSubject<Int?>

, but IntelliJ is insisting that I have to pass an Int to onNext

I am not an expert on RxJava but as far as I remamber you cannot pass null. I guess that this is why there is

@NotNull

annotation before

onNext

argument and this is why you have this problem.

@redrield RxJava does not support nullable types, use

Optional

thanks

Generally if you are convinced that you want to pass sth nullable to sth that is annotated as not nullable you need to write a proxy method using java

in rxjava 1.x you could pass

null

, in rxjava 2.x you can't pass null through streams by design (i assume youre using 2.x)