【Java笔记】利用java8新特性和递归实现多级菜单

public List<CategoryEntity> listWithTree() {

    List<CategoryEntity> entities = baseMapper.selectList(null);

    List<CategoryEntity> level1Menus = entities.stream().filter(categoryEntity -> {
        return categoryEntity.getParentCid() == 0;
    }).map((menu)->{
        menu.setChildren(getChildren(menu,entities));
        return menu;
    }).sorted((menu1,menu2)->{
        return (menu1.getSort()==null?0:menu1.getSort()) - (menu2.getSort()==null?0: menu2.getSort());
    }).collect(Collectors.toList());

    return level1Menus;
}

private 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());
    }).collect(Collectors.toList());

    return children;
}