typealias foo = () -> Unit

Also note that this feature works only for Java interop; since Kotlin has proper function types, automatic conversion of functions into implementations of Kotlin interfaces is unnecessary and therefore unsupported.

public class Foo {
    private final Predicate<File> isChild = file -> file != null && (roots.contains(file) || this.isChild.test(file.getParentFile()));
}

class Foo {
        private val isChild:(File) -> Boolean = { f ->  roots.contains(f) || isChild(f.parentFile)}
}

lateinit

Error:(26, 5) Kotlin: 'lateinit' modifier is allowed only on mutable properties
Error:(26, 5) Kotlin: 'lateinit' modifier is not allowed on properties with initializer

class Foo {
    private lateinit var isChild:(File) -> Boolean
    
    init {
        isChild = { f ->  roots.contains(f) || isChild(f.parentFile)}
    }
}

let

String?

let

Any?

null

?.

run

let

x?.get(0)

@JvmStatic

'MY_STATIC_ARRAY' has private access in 'ClassA'

@JvmField

@JvmStatic

object

@JvmStatic