docs: public static boolean isAlphaNumericOrContainsOnlyCharacters(String in, String chars) {
  		char c = 0;
  		for (int i = 0; i < in.length(); i++) {
  			c = in.charAt(i);
  			if (Character.isLetterOrDigit(c) == (chars.indexOf(c) != -1)) {
  				return false;
  			}
  		}
  		return true;
  	}