Best Rx Fibonacci

Fibonacci.kt

import io.reactivex.Observable
import org.junit.Test
import java.util.*

class Fibonacci {
    
    fun main(args: Array<String>) {
        val fibonacci = fibonacci(7)
        val disposable = fibonacci.subscribe { integer -> println(integer) }
    }

    private fun fibonacci(index: Int): Observable<Int> {
        return Observable.range(1, 1).repeat(index.toLong()).scan(ArrayList(Arrays.asList(0, 1))
        ) { list, _ ->
            list.add(list[list.size - 2] + list[list.size - 1])
            list.removeAt(0)
            list
        }.map { list -> list[list.size - 1] }
    }
}