隨機數生成器問題

Question

我的問題是下面的代碼是否正確地生成了一個隨機數，如在最近20次嘗試中我得到500 000次5次，這根本沒有反映出獲得它的2％的機會...

  public static int randInt(int min, int max) {

        // NOTE: Usually this should be a field rather than a method
        // variable so that it is not re-seeded every call.
        Random rand = new Random();

        // nextInt is normally exclusive of the top value,
        // so add 1 to make it inclusive
        int randomNum = rand.nextInt((max - min) + 1) + min;

        return randomNum;
    }

    public void prizegenerator(View v) {
        int fate = randInt(0,100);
        int reward=0;
        if (fate <= 30) {
            reward = 1000;
        }
        else if (fate <= 50) {
            reward = 2000;
        }
        else if (fate <= 80) {
            reward = 5000;
        }
        else if (fate <=90) {
            reward =  10000;
        }
        else if (fate <= 95) {
            reward = 50000;
        }
        else if (fate <= 97) {
            reward = 100000;
        }
        else if (fate <= 99) {
            reward = 500000;
        }
        else if (fate <= 100) {
            reward = 1000000;
        }

Answer 1

我將您的代碼綁定到簡單的main方法中，並且可以正常工作。 自己嘗試：

public static void main(String[] args) {
    Main main = new Main();
    List<Integer> list = new ArrayList<Integer>();
    for (int i = 0; i < 100; i++) {
        list.add(main.prizegenerator());
    }
    Collections.sort(list);

    for (Integer integer : list) {
        System.out.println(integer);
    }
}

當我多次運行它時，它生成的大多數是500000的2倍，與您2％的機率相匹配（98和99）