Fibonacci in Kotlin

Fibonacci.kt

package tm.alashow.homework.datastructures.second.kt

import java.math.BigInteger

fun main(args: Array<String>) {
    Fibonacci.init()
}

object Fibonacci {

    fun init() {
        // forever and ever
        while (true) {
            print("Enter Fn: ")

            val n = try { readLine()!!.toLong() } catch (e: Exception) { 10L }

            println("\nFibonacci '$n': ")

            // seed is 0 and 1
            fibonacci(BigInteger.ZERO, BigInteger.ONE, BigInteger.valueOf(n))

            //double space
            println("\n")
        }
    }

    /**
     * Calculates and prints each step of Fibonacci using tail recursion.
     *
     * tailrec modifier used to use tail recursion optimization.
     */
    tailrec private fun fibonacci(a: BigInteger, b: BigInteger, n: BigInteger): BigInteger {
        print("$a, ")
        return if (n == BigInteger.ZERO) a else fibonacci(b, a + b, n - BigInteger.ONE)
    }
}