точка

gistfile1.txt

    public static void main(String[] args) {
        double average = 0;
        int count = 0;
        for (int i = 0; i < 1_000_000; i++) {
            average += enhance(10, 15, Scroll.REGULAR);
            count++;
        }
        System.out.println("Average : " + average / count);

        average = 0;
        count = 0;
        for (int i = 0; i < 1_000_000; i++) {
            average += enhance(10, 15, Scroll.BLESSED);
            count++;
        }
        System.out.println("Average for blessed : " + average / count);

    }

    private static int enhance(int from, int to, Scroll scroll) {
        int attempts = 0;
        int currentLevel = from;

        while (currentLevel < to) {
            currentLevel += tryWith(currentLevel, scroll);
            attempts++;
        }
        return attempts;
    }

    static int tryWith(int currentLevel, Scroll scroll) {
        double random = ThreadLocalRandom.current().nextDouble();

        //45% chance of success
        if (currentLevel == 10) {
            return random >= 0.45 ? 0 : scroll.levelUp();
        }

        //45% chance of success
        if (currentLevel == 11 || currentLevel == 12) {
            return random >= 0.45 ? -1 : scroll.levelUp();
        }

        //40% chance of success
        if (currentLevel == 13 || currentLevel == 14) {
            return random >= 0.40 ? -1 : scroll.levelUp();
        }

        throw new RuntimeException("not supported");
    }

    private enum Scroll {
        REGULAR,
        BLESSED;

        public int levelUp() {
            switch (this) {
                case BLESSED:
                    return ThreadLocalRandom.current().nextInt(1, 4);
                default:
                    return 1;
            }
        }
    }