generic top-k collector in Kotlin

top.kt

import java.util.PriorityQueue
import java.util.stream.Collector
import java.util.stream.Collector.Characteristics


fun <T : Comparable<T>> topN(n: Int) = Collector.of(
        { PriorityQueue<T>(n + 1) },
        { queue, value: T ->
            queue.add(value)
            if (queue.size > n) {
                queue.poll()
            }
        },
        { first, second ->
            for (value in second) {
                first.add(value)
                if (first.size > n) {
                    first.poll()
                }
            }
            first
        },
        { queue -> queue.sortedDescending() },
        arrayOf(Characteristics.UNORDERED)
)