公平概率抽奖算法工具类分享

• 支持按概率权重抽奖
• 支持奖品动态增减
• 支持泛型传参
• 返回奖品

依赖hutool工具类，可进一步改造成带库存的奖品，我这里暂时用不到库存就不改造了，有大佬改造好了请留言~

工具类

    /**
     * 抽奖，返回抽到的奖品
     * @param prizeList 奖品列表
     * @return T
     * @exception
     * @author GMQ
     * @date 2022/2/18 21:18
     **/
    public static <T> T lottery(List<T> prizeList){
        if (CollUtil.isEmpty(prizeList)){
            return null;
        }
        //概率总和
        BigDecimal rateSum = BigDecimal.ZERO;
        for (T t1 : prizeList) {
            Map map = Convert.convert(HashMap.class, t1);
            rateSum = NumberUtil.add(rateSum,NumberUtil.toBigDecimal(map.get("winnRate")+""));
        }

        BigDecimal temp = BigDecimal.ZERO;
        //比值
        List<BigDecimal> tempList = new ArrayList<>(prizeList.size());
        for (T t1 : prizeList) {
            Map map = Convert.convert(HashMap.class, t1);
            temp = temp.add(NumberUtil.toBigDecimal(map.get("winnRate")+""));
            tempList.add(NumberUtil.div(temp,rateSum,8));
        }
        BigDecimal value = NumberUtil.round(RandomUtil.randomBigDecimal(),8);
        tempList.add(value);
        Collections.sort(tempList);
        int index = tempList.indexOf(value);

        T win = prizeList.get(index);
        return win;
    }

使用示例

    @Test
    void f5(){
        List<Map> list = new ArrayList<>();
        Map map1 = new HashMap();
        map1.put("name","现金红包200");
        map1.put("winnRate","47");
        list.add(map1);
        Map map2 = new HashMap();
        map2.put("name","小米运动手表");
        map2.put("winnRate","30");
        list.add(map2);
        Map map3 = new HashMap();
        map3.put("name","手机");
        map3.put("winnRate","10");
        list.add(map3);
        Map map4 = new HashMap();
        map4.put("name","苹果电脑");
        map4.put("winnRate","5");
        list.add(map4);
//        Map map5 = new HashMap();
//        map5.put("name","三亚五日游");
//        map5.put("winnRate","1");
//        list.add(map5);

        BigDecimal rateSum = BigDecimal.ZERO;
        for (Map map : list) {
            rateSum = NumberUtil.add(rateSum,NumberUtil.toBigDecimal(map.get("winnRate")+""));
        }
        System.out.println("概率总和："+rateSum);

        Map map = new HashMap();
        // 抽取100次
        for (int i = 0; i < 100; i++) {
            Map win = LotteryUtil.lottery(list);
            map.put(win.get("name"),map.get(win.get("name"))==null?1:Integer.valueOf(map.get(win.get("name"))+"")+1);
        }
        System.out.println("抽中统计："+JSON.toJSONString(map));

    }