Value classes in generics - interoperability with Java/Groovy


I’m struggling with value classes in generics and interoperability with Java or Groovy. Value class are inlined: Inline classes | Kotlin except for generics.

Given following value class and interface (Kotlin):

value class ValueClass(val id: String)

interface ValueClassListProvider {
    fun values(): List<ValueClass>

    fun value(): ValueClass

how can I implement ValueClassListProvider interface in Java or Groovy?

class ValueClassListProviderImplJava implements ValueClassListProvider {
    public List<ValueClass> values() {
        return Arrays.asList(new ValueClass("1"));

    public String value() {
        return "1";

Trying to run following code:

    public static void main(String[] args) {
        ValueClassListProviderImplJava provider = new ValueClassListProviderImplJava();

result in:

java: cannot find symbol
  symbol:   constructor ValueClass(java.lang.String)
  location: class pl.test.valueclass.ValueClass

For Groovy implementation of ValueClassListProvider interface:

class ValueClassListProviderImplGroovy implements ValueClassListProvider {

    List<String> values() {
        return ["1", "2"]

    String value() {
        return "1"

it compiles and seems to work, but when this implementation is later used in Kotlin code (suppose this is stub used in spock tests), it blows with:

java.lang.ClassCastException: class java.lang.String cannot be cast to class pl.test.valueclass.ValueClass

Is it possible to create instance of value class in Java or Groovy (needed for generics)?