java 8 递归 并且根据某个字段排序

1.实体bean结构

public class DmpDictVo {
    @ApiModelProperty(value = "数据id")
    private String id;

    @ApiModelProperty(value = "父id")
    private String pid;

    @ApiModelProperty(value = "描述")
    private String name;

　　//初始化 children 避免报空指针异常

    List<DmpDictVo> children = new ArrayList<>();
}

// 根据自己的业务编写
private List<DmpDictVo> searchFatherDmpDict() {
　// 查询出所有的数据字典

List<QaCategoryVo> qaCategoryVoList = findAll(type);
// 递归封装数据

return makeTree(qaCategoryVoList, -1L);

 */

private List<QaCategoryVo> makeTree(List<QaCategoryVo> departmentList, Long pId) {

    //子类
    List<QaCategoryVo> children = departmentList.stream().filter(x -> x.getPid().equals(pId)).collect(Collectors.toList());
    // 排序
    children = children.stream().sorted(Comparator.comparing(QaCategoryVo::getSort, Comparator.nullsLast(Integer::compareTo)).reversed()).collect(Collectors.toList());
　　
    if(children.isEmpty()){
        return null;
    }
    //后辈中的非子类
    List<QaCategoryVo> successor = departmentList.stream().filter(x -> !x.getPid().equals(pId)).collect(Collectors.toList());

    for (QaCategoryVo x : children) {
        List<QaCategoryVo> qaCategoryVos = makeTree(successor, x.getId());
        x.setChildren(qaCategoryVos);
    }
    return children;

}