Scala for, foreach, while, tailrec comparison

Test.scala

import java.util._
import java.io._
import java.util

import scala.annotation.tailrec

object Test {

  var out: PrintWriter = null
  var br: BufferedReader = null
  var st: StringTokenizer = null
  val upperBound = Integer.MAX_VALUE / 100

  def next: String = {
    while (st == null || !st.hasMoreTokens) {
      st = new StringTokenizer(br.readLine)
    }
    return st.nextToken
  }

  def nextInt: Int = {
    return Integer.parseInt(next)
  }

  def nextLong: Long = {
    return java.lang.Long.parseLong(next)
  }

  @tailrec
  def recursion(i: Int): Unit = {
    if (i < Test.upperBound) {
      val z: Double = Math.pow(i, 2000)
      if (z % 234541 == 0) {
        println(z)
      }
      recursion(i + 1)
    }
  }


  def solve: Int = {
    val start1 = System.currentTimeMillis()
    (0 until upperBound).foreach({
      x =>
        val z: Double = Math.pow(x, 2000)
        if (z % 234541 == 0) {
          println(z)
        }
    })
    out.println(".foreach " + (System.currentTimeMillis() - start1))
    val start2 = System.currentTimeMillis()
    for (i <- 0 until upperBound) {
      val z: Double = Math.pow(i, 2000)
      if (z % 234541 == 0) {
        println(z)
      }
    }
    out.println("for " + (System.currentTimeMillis() - start2))
    val start3 = System.currentTimeMillis()
    var i = 0
    while (i < upperBound) {
      val z: Double = Math.pow(i, 2000)
      if (z % 234541 == 0) {
        println(z)
      }
      i += 1
    }
    out.println("while " + (System.currentTimeMillis() - start3))
    val start4 = System.currentTimeMillis()
    i = 0
    recursion(i)
    out.println("tailrec " + (System.currentTimeMillis() - start4))
    return 1
  }

  def main(args: Array[String]): Unit = {
    br = new BufferedReader(new InputStreamReader(System.in))
    out = new PrintWriter(new BufferedOutputStream(System.out))
    solve
    out.close
  }
}