Guys, I have a very weird Java / Kotlin interoperability problem with the `Boolean` type. I’m using ...

# getting-started

[svenjacobs]

Guys, I have a very weird Java / Kotlin interoperability problem with the Boolean type. I’m using a Java API which defines two functions: void setSomething(boolean enabled) and void setSomething(Boolean enabled), where Boolean is java.lang.Boolean here. The first function with the primitive Java type is marked deprecated. I’m trying to call the second function from Kotlin code but every time Kotlin tries to unbox the boolean into the primitive type, so it calls the deprecated function. How can I force Kotlin to use the boxed object type?

For example I tried

api.setSomething(Boolean.valueOf(true))

but it’s still complaining.

[Vampire]

Just a guess, but maybe true as java.lang.Boolean?

[svenjacobs]

Unfortunately not, this gives a type error

Required: kotlin.Boolean
Found: java.lang.Boolean

[svenjacobs]

and true as Boolean is just marked as an obsolete cast, still tries to call the deprecated function.

[Vampire]

Maybe true as Boolean??

[svenjacobs]

Yes, that’s it! Thank you!

[svenjacobs]

It’s been so long since I last coded Java. I totally forgot that every object reference is nullable by default there 😅

[phldavies]

It’s worth keeping in mind that Kotlin/JVM treats Boolean as the unboxed boolean primitive and Boolean? as the boxed java.lang.Boolean (see here). Similarly to numbers.