Java中将List转为树形结构

Stream流处理

    @Override
    public List<CategoryEntity> listWithTree() {
        // 1、查出所有分类
        List<CategoryEntity> entities = baseMapper.selectList(null);

        // 组装成父子的树形结构

        return entities.stream().filter(m1 ->
            m1.getParentCid() == 0
        ).peek(menu -> {
            menu.setChildren(getChildren(menu, entities));
        }).sorted((menu1,menu2)->{
            return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());
        }).collect(Collectors.toList());
    }

    private List<CategoryEntity> getChildren(CategoryEntity root, List<CategoryEntity> all) {
        return all.stream().filter(m1 -> {
            return m1.getParentCid().equals(root.getCatId());
        }).peek(m1 -> {
            m1.setChildren(getChildren(m1, all));
        }).sorted((menu1,menu2)->{
            return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());
        }).collect(Collectors.toList());
    }

@GetMapping("/getorganddep")
    @ApiOperation(value = "获取机构与部门列表")
    public ResultData<GetDepartmentVO> getOrgAndDep(UserContext user) {
        GetDepartmentVO vo = new GetDepartmentVO();
        Organization organization = orgRemoteService.get(user.getOrgId());
        BeanUtils.copyProperties(organization, vo);

        List<QueryCriteria> collection = new ArrayList<>();
        collection.add(new QueryCriteria("ancestors", QueryCriteria.LIKE, user.getOrgId()));
        List<Department> departments = departmentService.list(collection);

        vo.setDepartments(departments.stream().filter(v -> v.getParentId().equals(user.getOrgId())).peek(t -> {
            t.setChilds(getChildren(departments, t.getId()));
        }).collect(Collectors.toList()));

        return ResultData.OK(vo);
    }

    private List<Department> getChildren(List<Department> departments, String parentId) {
        return departments.stream().filter(v -> {
            return v.getParentId().equals(parentId);
        }).peek(t -> {
            t.setChilds(getChildren(departments, t.getId()));
        }).collect(Collectors.toList());
    }