public String getCoverBottom(FlowAdditions additions) {
        if(null==additions){
            return "默认";
        }
        List<FlowCoverBottom> li = this.isMatchBottom(additions);
        if(null == li || li.isEmpty()){
            return "默认";
        }
        //根据权重输出兜底方。
        int sum = li.stream().mapToInt(FlowCoverBottom::getIntRatio).sum();
        int random = RandomUtils.nextInt(0, sum);
        ConcurrentSkipListMap<Integer,String> skipListMap = new ConcurrentSkipListMap<>();
        int ceiling = 0;
        for(int i=0;i<li.size();i++){
            FlowCoverBottom bottom = li.get(i);
            ceiling = ceiling+bottom.getIntRatio();
            skipListMap.put(ceiling,bottom.getCode());
        }
        return skipListMap.higherEntry(random).getValue();
    }