public void shuffleLetters(){
        Random gen = new Random();
        ArrayList<String> chars = new ArrayList<String>();
        for (int i = 0; i < letters.length(); i++)
            chars.add(letters.substring(i,i+1));
        String s = "";
        for (int j = 0; j < letters.length(); j++){
            int x = gen.nextInt(chars.size());
            s += chars.remove(x);
        }
        shuffledLetters = s;
    }