Hi! Anyone knows why Kotlin can’t invoke Java meth...

# server

[Bo Zhang]

Hi! Anyone knows why Kotlin can’t invoke Java method with Function parameters?

[Vampire]

What does the error say if you hover over the red-underlined part?

[Bo Zhang]

image.png

[Vampire]

Works fine here in Kotlin REPL

[Vampire]

val f: java.util.function.Function<String, String> = java.util.function.Function { it }
 foo.Main.from(f)
res2: kotlin.collections.(Mutable)Map<kotlin.String!, kotlin.String!>! = {}

[Vampire]

Ah, interesting, with CacheLoader it does not work

[Vampire]

I tried before with

public static <K, V> Map<K, V> from(Function<K, V> function) {
        return emptyMap();
    }

[Bo Zhang]

Yes. It seems to be an interoperability issue.

[Vampire]

I had that method in a Java class

[Mike Carlin]

Are you using the Function class from guava or the java.util?

[Bo Zhang]

From java.util.function, you can see that at the top of the source code.

[Vampire]

Ah, the from method expects a Guava Function though, not a Java Function

[Vampire]

This works fine:

com.google.common.cache.CacheLoader.from<String, String> { it }

[Vampire]

As well as this:

val f: com.google.common.base.Function<String, String> = com.google.common.base.Function { it }
com.google.common.cache.CacheLoader.from(f)

[Bo Zhang]

Ah, thanks! Stupid question!

[Vampire]

Stupid same-named interfaces

[ephemient]

well the Guava one came first. IIRC they were going to transition to the Java interfaces, but I haven't been keeping track of where that is