code: public static String randomString(int length) {
          Preconditions.checkArgument(length > MIN_PASSWORD_LENGTH, "random string length must be at least 1 character");
          Preconditions.checkArgument(length <= MAX_PASSWORD_LENGTH, "random string length must be at most 256 character");
          
          return RandomStringUtils.random(length, 0, CHARACTERS.length-1, false, false, CHARACTERS, new SecureRandom());
      }
docs: Generates a random string with the given length.
  
  Based on commons-lang3 RandomStringUtils using SecureRandom
  
  Uses: uppercase letters, lowercase letters and numbers
  
  @param length The length of the random string
  @return A random String