public double getNgramsEntropy(String text, int n) throws FileNotFoundException {
        PrintStream ps = new PrintStream("log" + n + ".txt");
        int amount = 0;
        double result = 0.0;
        int length = text.length();
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < length - n + 1; i++) {
            for(int j = 0; j < n; j++) {
                sb.append(text.charAt(i + j));
            }
            if(stringMap.containsKey(sb.toString())) {
                stringMap.put(sb.toString(), stringMap.get(sb.toString()) + 1.0);
            }
            else {
                stringMap.put(sb.toString(), 1.0);
            }
            sb.delete(0, sb.length());
        }
        for(Entry<String, Double> item: stringMap.entrySet()) {
            amount += item.getValue();
        }
        for(Entry<String, Double> item: stringMap.entrySet()) {
            stringMap.put(item.getKey(), (double)item.getValue() / amount);
            result -= item.getValue() * (Math.log(item.getValue()) / Math.log(2));
            ps.println(item.getKey() + " / " + item.getValue() + " / " + (Math.log(item.getValue()) / Math.log(2)) + " / " + item.getValue() * (Math.log(item.getValue()) / Math.log(2)));
        }
        stringMap.clear();
        ps.println();
        return result / n;
    }