Scalaでリストに要素を追加する処理をmutable/immutableで比較してみた

Benchmark.scala

package util

import java.util.Date
import scala.collection.mutable.ListBuffer
import scala.collection.mutable.MutableList

object Benchmark {

  val END = 10000000

  def main(args: Array[String]) {

    benchmark("a")(aTest)
    benchmark("b")(bTest)
    benchmark("c")(cTest)
    println("---")
    benchmark("a")(aTest)
    benchmark("b")(bTest)
    benchmark("c")(cTest)
    println("---")
    benchmark("a")(aTest)
    benchmark("b")(bTest)
    benchmark("c")(cTest)
    println("---")
    benchmark("a")(aTest)
    benchmark("b")(bTest)
    benchmark("c")(cTest)
    println("---")
    benchmark("a")(aTest)
    benchmark("b")(bTest)
    benchmark("c")(cTest)
    println("---")

  }

  def benchmark[R](s: String)(f: => R): R = {
    val start = new Date().getTime
    val r = f
    val end = new Date().getTime
    println(s + " " + (end - start) + " msec.")
    r
  }

  def aTest(): List[Int] = {
    var result: List[Int] = Nil
    for (i <- (0 to END)) {
      result = i :: result
    }
    result
  }

  def bTest(): ListBuffer[Int] = {
    val result: ListBuffer[Int] = new ListBuffer
    for (i <- (0 to END)) {
      result += i
    }
    result
  }

  def cTest(): MutableList[Int] = {
    val result: MutableList[Int] = new MutableList
    for (i <- (0 to END)) {
      result += i
    }
    result
  }

}

// -- RESULTS -- //
// a 8715 msec.
// b 4987 msec.
// c 3734 msec.
// ---
// a 3365 msec.
// b 3740 msec.
// c 5886 msec.
// ---
// a 1170 msec.
// b 5762 msec.
// c 3289 msec.
// ---
// a 4963 msec.
// b 2392 msec.
// c 5808 msec.
// ---
// a 1328 msec.
// b 5837 msec.
// c 3520 msec.
// ---