Java's

Map.computeIfAbsent()

function documentation includes:

Copy code

If the mapping function returns {@code null}, no mapping is recorded.

However, when calling this function from Kotlin code, the mapping function has a signature

(K) -> V

, meaning that the passed in function cannot return

null

. Is there any way to use

computeIfAbsent

from kotlin passing a function which may return

null

?

this does seem a bit odd to me -- Kotlin allows

null

for

compute

and

computeIfPresent

. Why the difference? the only difference in signature is that they're

BiFunction

rather than

Function

It seems it was a deliberate decision relating to Java's Map: https://discuss.kotlinlang.org/t/why-is-the-result-of-the-computeifabsent-lambda-non-nullable/19463

Thanks for the replies, I ran across that discuss thread as well and though it seems like a strange decision. Not necessarily a bad one, but odd to have a case where the same function can't be used in the same ways from Kotlin as from Java. I ended up replacing the call with the

compute

function.