n-digit Verification Code Generator

This is a verification code generator, which generates n-digit numeric strings. (code can be 0000, so I chose String as a return type rather than Int or Long.)

It'll be great if anyone review this code and suggest more elegant or scalaish solution.

import scala.util.Random

object VerificationCodeGenerator {
  val rand = new Random

  def generate(digit: Int): String = {
    val sb = new StringBuilder
    for (i <- 1 to digit) {
      sb.append(rand.nextInt(10))
    }
    sb.toString()
  }
}

if your number of digits is always going to be less than about 10, then you can use a single random operation and a string format, to do all the work without the loop.

Consider a method like:

def generate(digit: Int): String = {
    var randVal = rand.nextInt(math.pow(10, digit).toInt)
    var fmt = "%0" + digit + "d"
    fmt.format(randVal)
}

The randVal pulls a value with the limited number of digits (perhaps fewer than the limit). The format operation 0-pads the value to the right number, though.

This is not so much a scala way of doing it, but it is closer, and probably more efficient.

I would consider creating instances to handle each length of digits to avoid having to create the format each time, though.

See it running in ideone

StackExchange Code Review Q#90015, answer score: 8