code: public static String getRandomString(final int size, final String stringSet) {
  
  		final StringBuilder buff = new StringBuilder(size);
  
  		for (int i = 0; i < size; i++) {
  			final char nextChar = stringSet.charAt(RAN.nextInt(stringSet.length()));
  			buff.append(nextChar);
  		}
  		return buff.toString();
  	}
docs: Creates a size byte long unicode string. All codes are from the set "stringSet"
  
  @param size
  number of characters in the return string
  @param stringSet
  set of characters used for string creation
  @return a random string build from "stringSet"