From the guide I know that

lateinit

vars cannot be primitive types. If you're trying to create a bean-compliant class, how do you designate an

Integer

or

Double

type? If you make the property type

Int

you get the error that primitive types can't be

lateinit

, if you give it the type

Integer

you get the warning that you shouldn't use

Integers

but should use

Int

.. And for

Double

there doesn't even appear to be a way to say you want the Object

Double

and not a primitive

double

IIRC

Int?

should always correspond to

Integer

, so you can use that. And you can create additional

@Transient

property with overriden

get()

and

set()

which would allow to avoid constant

!!

-ing. Not the best solution, but should work. Maybe someone could suggest better options though.

I was hoping to not have nullable fields

Well, docs (https://kotlinlang.org/docs/reference/java-interop.html) specifically mention when boxed types are used, and the topic (https://discuss.kotlinlang.org/t/force-hint-of-int-to-java-lang-integer/2441) doesn't have anything useful either. If you stick with wrapper property as I suggested you won't have to deal with nullable property in most of the code anyway.

If you need to do this a lot maybe write a delegate for it?

I would think that making a class that can be used where a bean is expected by a java library would be a common thing.

@karelpeeters, are you sure there is a way to use delegated property in a bean class? I'm not very good in specifics of desktop Java but I definitely remember there was some case in Android where delegated property couldn't be used, probably required actual backing field or something.

Otherwise, you're right, that wouldn't work.