I want a groovy simple code that generates Random number

I want a groovy simple code that generates Random number, and i don't want to add random number generator

Currently i am using:

import org.apache.commons.lang.RandomStringUtils

log.info getRandomNumber(8)

def getRandomNumber(int num)
{
       String charset = (('1'..'9')).join()
       def randValue = RandomStringUtils.random(num, charset)
       while (randValue.size()!=num)
      {
              randValue = RandomStringUtils.random(num, charset)
       }
       return randValue
}

Any alternate or better solution for this?