Scala String to Long check via regex vs cast

stringToLong.scala

def time[A](a: => A) = {
  val now = System.nanoTime
  val result = a
  val micros = (System.nanoTime - now) / 1000
  println("%d microseconds".format(micros))
  result
}

def validIdByRegex(id: String): Boolean = {
  val idPattern = """[0-9]+""".r
  idPattern.pattern.matcher(id).matches()
}

def validIdByCast(id: String): Boolean = {
  try {
    id.toLong
    true
  } catch {
    case e: Throwable => false
  }
}

def randomString(characters: String)(n: Int): String = 
  Stream.continually(scala.util.Random.nextInt(characters.size)).map(characters).take(n).mkString
 
def randomSometimesIdString(n: Int) = 
  randomString("abcd0123456789")(n)

val userIds = (0 until 1000) map { _ => randomSometimesIdString(10) }
println("validate by regex")
time {
   userIds map {userId => 
     validIdByRegex(userId)
   }
}

println("validate by cast")
time {
   userIds map {userId => 
     validIdByCast(userId)
   }
}

// results
// validate by regex
// 29033 microseconds
// validate by cast
// 13845 microseconds

For anyone accidentally finding this - it's non conclusive

• regex is being compiled all over again
• no warm up runs
• no GC handling

Please do not make any conclusions based on this.

Just by extracting the regex out of the function you will get something like

validate by regex
8609 microseconds
validate by cast
11394 microseconds