regex_test.scala

object Main {
  def main(args: Array[String]) = {
    val data = testData()

    val start1 = System.currentTimeMillis()
    data.foreach(isValidIpFormat1)
    val end1 = System.currentTimeMillis()
    println("1: " + (end1 - start1))

    val start2 = System.currentTimeMillis()
    data.foreach(isValidIpFormat2)
    val end2 = System.currentTimeMillis()
    println("2: " + (end2 - start2))

    var n = 0
    data.foreach { x =>
      require(isValidIpFormat1(x) == isValidIpFormat2(x))
      if (isValidIpFormat1(x)) n += 1
    }
    println("valid: " + n)
  }
  def testData(): Seq[String] = {
    var i = 0
    val ret = scala.collection.mutable.ArrayBuffer[String]()
    val r = new scala.util.Random()
    while (i < 1000000) {
      val x = r.nextInt(5)
      if (x == 4) {
        ret +=
          r.nextInt(300).toString + "." +
          r.nextInt(300).toString + "." +
          r.nextInt(300).toString + "." +
          r.nextInt(300).toString
      } else if (x == 3) {
        ret +=
          r.nextInt(300).toString + "." +
          r.nextInt(300).toString + "." +
          r.nextInt(300).toString
      } else if (x == 2) {
        ret +=
          r.nextInt(300).toString + "." +
          r.nextInt(300).toString
      } else if (x == 1) {
        ret +=
          r.nextInt(300).toString
      }
      i += 1
    }
    ret
  }

  private[this] def isDigit(c: Char): Boolean = {
    '0' <= c && c <= '9'
  }
  def isValidIpFormat1(ip: String): Boolean = {
    val ipArray: Array[String] = ip.split("\\.")
    if (ipArray.length != 4) { return false }
    var i = 0
    while (i < 4) {
      val s = ipArray(i)
      if (s.size == 3) {
        if (s(0) == '2') {
          if (s(1) == '5') {
            if (! ('0' <= s(2) && s(2) <= '5')) { return false }
          } else if ('0' <= s(1) && s(1) <= '4') {
            if (! isDigit(s(2))) { return false }
          } else {
            return false
          }
        } else if ('0' <= s(0) && s(0) <= '1') {
          if (! isDigit(s(1))) { return false }
          if (! isDigit(s(2))) { return false }
        } else {
          return false
        }
      } else if (s.size == 2) {
        if (! isDigit(s(0))) { return false }
        if (! isDigit(s(1))) { return false }
      } else if (s.size == 1) {
        if (! isDigit(s(0))) { return false }
      } else {
        return false
      }
      i += 1
    }
    return true
  }
  val pattern = java.util.regex.Pattern.compile(
    "^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
    "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
    "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
    "([01]?\\d\\d?|2[0-4]\\d|25[0-5])$"
  )
  def isValidIpFormat2(ip: String): Boolean = {
    pattern.matcher(ip).matches()
  }
}

result.txt

$ for i in `seq 10`; scala Main
1: 647
2: 359
valid: 105767
1: 354
2: 395
valid: 106295
1: 668
2: 392
valid: 105741
1: 650
2: 384
valid: 106096
1: 662
2: 382
valid: 106424
1: 673
2: 428
valid: 106588
1: 686
2: 381
valid: 106354
1: 642
2: 383
valid: 105919
1: 342
2: 403
valid: 105998
1: 685
2: 393
valid: 106096