From J to K

1_pure.java

// Write Once Read Never
Map<Double , Tuple2<Star , StationaryType>> map = stars
  .stream()
  .flatMap(star -> {
    List<Tuple2<Double , StationaryType>> list = getPeriodStationary(star, fromGmt, toGmt, starPositionImpl);
    return list.stream().map(t -> Tuple.tuple(t.v1() , star , t.v2()));
  }).collect(Collectors.toMap(Tuple3::v1, t -> Tuple.tuple(t.v2() , t.v3()) , (v1, v2) -> v1 , TreeMap::new));

return map.entrySet().stream()
  .map(entry -> Tuple.tuple(entry.getKey() , entry.getValue().v1() , entry.getValue().v2()))
  .collect(Collectors.toList());

2_translatedKotlin.kt

// Translated by IntelliJ 
// convert Tuple2/Tuple3 to Pair/Triple
// WORKING , But WTF

val map = stars
  .stream()
  .flatMap { star ->
    val list = getPeriodStationary(star, fromGmt, toGmt, starPositionImpl)
    list.stream().map { (first, second) -> Triple(first, star, second) }
  }.collect<TreeMap<Double, Pair<Star, StationaryType>>, Any>(Collectors.toMap(Function<Triple<Double, Star, StationaryType>, Double> { it.getFirst() }, { (_, second, third) -> Pair(second, third) }, { v1, (first, second) -> v1 }, Supplier<TreeMap<Double, Pair<Star, StationaryType>>> { TreeMap() }))
return map.entries.stream()
  .map { entry -> Triple(entry.key, entry.value.first, entry.value.second) }
  .collect<List<Triple<Double, Star, StationaryType>>, Any>(Collectors.toList())  

3_pureKotlin.kt

// Concise & Slick
return stars.flatMap { star ->
  getPeriodStationary(star , fromGmt , toGmt , starPositionImpl)
    .map { (gmt , type) -> Triple(gmt , star , type) }
  }.sortedBy { triple -> triple.first }