what does

expect

and

actual

translate to in java eg

expect fun getPlatformName(): String

actual fun getPlatformName(): String {
    return "Desktop"
}

https://kotlinlang.org/docs/multiplatform-connect-to-apis.html#rules-for-expected-and-actual-declarations expect/actual are language keywords and not visible in the resulting target code.

hmm ok could i do the same thing in Java ?

Java doesn’t have different platform targets, so I don’t believe there is an equivalent. It’s all JVM bytecode

alright

expect/actual are used for Kotlin Multiplatform only to enable consuming a common declaration in your common code.

🙂

Why can’t you mix java and Kotlin in the same module?

The best analogy is

interface

and

class

but it is not a translation but only another implementation of a similar concept.

it doesnt seem to compile the java code for some reason (class def not found)

Have you set up the java plugin or added withJava to your jvm block in the kotlin block?

i dont think so

kotlin {
    jvm {
        withJava()
    }
}

Note you can’t have this and an android target in the same module.

so for example, i cannot put it in this?

plugins {
    kotlin("multiplatform")
    id("org.jetbrains.compose")
    id("com.android.library")
}

kotlin {
    android()
    jvm("desktop") {
        jvmToolchain(11)
    }
    sourceSets {
        val commonMain by getting { dependencies { ... } }
        val androidMain by getting { dependencies { ... } }
        val desktopMain by getting { dependencies { ... } }
    }
}

android {
    namespace = "smallville7123.lua.jit.kotlin.common"
    compileSdkVersion(33)
    sourceSets["main"].manifest.srcFile("src/androidMain/AndroidManifest.xml")
    defaultConfig {
        minSdkVersion(24)
        targetSdkVersion(33)
    }
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
    }
}

You can try, but the android plugin and the java plugin are incompatible. Why do you need Java code? IntelliJ can convert it to Kotlin.

easier to write in java 🙂

You won’t be able to expect/actual like that. I’d create an interface, then implement it in each platform and pass in a factory or something.

true, but i should be able to expect/actual via seperate kotlin + java modules eg

kotlin-impl-bindings-desktop
java-impl-desktop

kotlin-impl-bindings-android
java-impl-android

however the

:common

module would require both

desktop

and

android

modules but i think it wont actually build both if only building for a single platform?

You could have your Kotlin module depend on your java module, then expect/actual creating it. Since you’re doing a Kotlin module anyway, I’d highly recommend learning to write in Kotlin directly instead of doing the Java modules.

alright