code: public final static String alphanumeric(final Random random, final int length)
  	{
  		final char[] buffer = new char[length];
  
  		for (int i = 0; i < length; i++)
  		{
  			final int rand = random.nextInt(36);
  			buffer[i] = digits[rand];
  		}
  
  		return new String(buffer);
  	}
docs: Generates a random sequence of alphanumeric characters of length <code>length</code> using the provided random number
  generator
  
  @param random
  the random number generator to use (must not be null)
  @param length
  the length of the string to generate (must be > 0)
  
  @return a new random alphanumeric String of length <code>length</code>