What can I pass to a Java method that expects a

Void!

?

Did you try

null

is the only thing that comes to my mind.

@Pablichjenkov Thank you! That works. I didn't think of that because of the

!

.

If memory serves, there is no instance of a

Nothing

type, null is the only value of a

Nothing?

type

Exactly, I missed the nullable mark

A void/Void in Java is

Unit

in Kotlin and has only one value

Unit

. Passing a null (

Unit?

) may indeed work as well. The type

Nothing

has no values at all (which means you can't create one, get one or pass one). The type

Nothing?

has only one value (null) and is a sub-type of all other types

T?

(including

Unit?

).

Java's

Void

is more like Kotlin

Nothing?

than

Unit

.

All Java methods returning the primitive

void

return

Unit

in Kotlin.

Void

is a nullable version of

void

in Java (much like

int

vs

Integer

), which would be

Unit?

in Kotlin.

Well primitive

void

is nothing like the class

Void

.

You're right about how

Void

is designed, with a private constructor and no public singleton or factory methods returning one, much like the design of

Nothing

.

In plain English, I would relate

Void

with Emptyness or

Nothing

. Don't know if the language designers pursued this semantic. Now as Anton said the fact of java methods returning

void

needing to return

Unit

in kotlin makes one to think that they are equivalent. To me this

void -> Unit

transformation is basically a trick to bridge an imperative paradigm with a functional paradigm. But when it comes to the typing system itself I am more into

Void

being more

Nothing

than

Unit

.

void

is not like

Nothing

at all, void simply means a function doesn't return anything but

Nothing

means it never returns!