Map - get or contains

import scala.collection.mutable

object HashTest {

  val imax = 10000

  def generateMap(imax: Int): mutable.HashMap[Int, String] = {
    val ret = scala.collection.mutable.HashMap.empty[Int, String]
    for (i <- 1 to imax) {
      ret.put(i * 2, (i * 2).toString)
    }
    ret
  }

  def test1(imax: Int)(map: mutable.HashMap[Int, String]): List[String] = {
    var ret = List[String]()
    for (i <- 1 to (imax * 2)) {
      if (map.contains(i)) {
        ret ::= map(i)
      } else {
        ret ::= ""
      }
    }
    ret
  }

  def test2(imax: Int)(map: mutable.HashMap[Int, String]): List[String] = {
    var ret = List[String]()
    for (i <- 1 to (imax * 2)) {
      map.get(i) match {
        case Some(in) => ret ::= in
        case None => ret ::= ""
      }
    }
    ret
  }

  def main(args: Array[String]) {
    for (i <- 1 to 7) {

      val k = Math.pow(10, i).toInt
      println(k + " sample in a map")
      var avrT1 = 0.0
      var avrT2 = 0.0
      for (j <- 1 to 1000) {
        val map = generateMap(k)
        val (_, t1) = time("contains") {
          test1(k)(map)
        }
        val (_, t2) = time("option") {
          test2(k)(map)
        }
        avrT1 += (t1 / 1000.0)
        avrT2 += (t2 / 1000.0)
      }
      println("  contains avr: " + avrT1 + " ns")
      println("  get avr:      " + avrT2 + " ns")
      println((if (avrT1 < avrT2) "contains" else "get") + " is faster with " + Math.abs(avrT1 - avrT2) + " ns")
      println()
    }
  }

  def time[R](name: String)(block: => R): (R, Long) = {
    val t0 = System.nanoTime()
    val result = block // call-by-name
    val t1 = System.nanoTime()
    //println(name + "Elapsed time: " + (t1 - t0) + "ns")
    (result, (t1 - t0))
  }
}