public static boolean isUniqueChars(String s) {
		// TODO Auto-generated method stub
		if (s.length()>256) return false;
		
		boolean[] ascii = new boolean[256];
		for (int i = 0; i < s.length(); i++) {
			if (ascii[s.charAt(i)]) return false; //should not be s.getChar!!!
			else ascii[s.charAt(i)] = true;
		}
		return true;
	}