以树状的形式封装有孩子的节点

@Override
    public List<CategoryEntity> listAsTree() {
        List<CategoryEntity> entities = baseMapper.selectList(null);
        List<CategoryEntity> level1Menus = entities.stream().filter(categoryEntity ->
                categoryEntity.getParentCid() == 0
        ).map((menu)->{menu.setChildren(getChildren(menu,entities));//收集之前处理再返回
            return menu;
        }).sorted((menu1,menu2)->{
            return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());//排序
        }).collect(Collectors.toList());
        return level1Menus;
    }

    public List<CategoryEntity> getChildren(CategoryEntity root,List<CategoryEntity> all){
        List<CategoryEntity> children = all.stream().filter((categoryEntity) -> {
            return categoryEntity.getParentCid() == root.getCatId();
        }).map(categoryEntity -> {
            categoryEntity.setChildren(getChildren(categoryEntity,all));
            return categoryEntity;
        }).sorted((menu1,menu2)->{
            return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());//排序
        }).collect(Collectors.toList());
        return children;
    }