scala_hash_map_test.scala

import scala.collection._
import scala.util.Random

object Utils {
  def time[A](name: String) (f: => Unit) = {
    val s = System.nanoTime
    f
    println(s"$name: ${((System.nanoTime - s) / 1e6).toLong} elapsed.")
  }
}

object Main {
  def main(args: Array[String]): Unit = {
    val source = Seq.fill(50000000){Random.nextInt()}.toArray
    val m = mutable.HashMap.empty[Int, Int]

    Utils.time("Insertion") {
      for (x <- source) {
        m.put(x, 0)
      }
    }

    Utils.time("Lookups") {
      var acc = 0
      for (x <- source)
        acc += m(x) % 10
      acc
    }
  }
}

// Insertion: 32627 elapsed.
// Lookups: 14824 elapsed.