How to translate Kotlin Nothing to Java?

Question

I have a class that is MyClass<T>

I need to subclass it to MySubclass<Nothing>

But sometimes I need to send a MyClass reference to a Java function, which in turn can receive MySubclass , How can I declare it so that it is compatible?

Or should I simply use void receiveClass(aClass: MyClass<*>) ?

Answer 1

If I understood your question correctly, you can do:

// Kotlin:
open class MyClass<T>
class MySubclass : MyClass<Nothing>()

// Java:
static <E> void receiveClass(MyClass<E> c) {
}

static void receiveClass1(MyClass<?> c) {
}

// Kotlin:
@JvmStatic
fun main(args: Array<String>) {
  receiveClass(MySubclass())
  receiveClass1(MySubclass())
}

Both variants will work and are equivalent during runtime, the difference is whether you need the type information <E> inside the receiveClass for type safety in compile time.