按权重随机排序 方案1，将list中每个实体的权重先取个随机值，然后在按随机后的权重排序。

public void sortList(List<Entity> list) {
        if(list == null){
            return;
        }
        list.forEach((Entity item) -> item.setWeight(random.nextInt(getWeight(item))));
        Collections.sort(list,(Entity item1,Entity item2) -> getWeight(item2)- getWeight(item1));
    }

        private int getWeight(Entity item) {
        Integer weight = item.getWeight();
        weight = weight==null ? 0 : weight;
        return weight;
    }