实现递归树形结构

模拟表中数据

实体类

@ApiModel(value = "树结构信息")
@Data
@AllArgsConstructor
public class TreeEntity {
 
    @ApiModelProperty("唯一id")
    private Integer id;
 
    @ApiModelProperty("名称")
    private String name;
 
    @ApiModelProperty("父类id")
    private Integer parentId;
 
    @ApiModelProperty("子节点集合")
    private List<TreeEntity> childNodeList;
}

模拟表中数据

    static List<TreeEntity>  listTree = new ArrayList<>();
    static {
        listTree.add(new TreeEntity(1,"爷",0,null));
        listTree.add(new TreeEntity(2,"二爷",0,null));
        listTree.add(new TreeEntity(3,"爷-爸",1,null));
        listTree.add(new TreeEntity(4,"爷-叔",1,null));
        listTree.add(new TreeEntity(5,"二爷-爸",2,null));
        listTree.add(new TreeEntity(6,"爷-爸-大儿子",3,null));
        listTree.add(new TreeEntity(7,"爷-爸-小儿子",3,null));
        listTree.add(new TreeEntity(8,"二爷-爸-大儿子",5,null));
        listTree.add(new TreeEntity(9,"二爷-爸-小儿子",5,null));
        listTree.add(new TreeEntity(10,"爷-叔-大儿子",4,null));
        listTree.add(new TreeEntity(11,"爷-叔-小儿子",4,null));
    }

递归实现：

   /**
     * 获取树结构
     * @return
     *  
     */
    @Override
    public List<TreeEntity> selectTree() {
        List<TreeEntity> leve1Menus = listTree.stream().filter(treeEntity ->
             treeEntity.getParentId() == 0
        ).map((menus) ->{
             menus.setChildNodeList(getChildNode(menus,listTree));
             return menus;
        }).collect(Collectors.toList());
        return leve1Menus;
    }
 
 
 
 
   /**
     * 递归子节点
     * @param root   当前单个菜单
     * @param allListTree   表中的所有菜单集合
     * @return
     */
    private List<TreeEntity> getChildNode(TreeEntity root, List<TreeEntity> allListTree){
 
        List<TreeEntity> ChildNodeList = allListTree.stream().filter((treeEntity) -> {
            return treeEntity.getParentId() == root.getId();
        }).map((treeEntity)->{
            treeEntity.setChildNodeList(getChildNode(treeEntity,allListTree));
            return treeEntity;
        }).collect(Collectors.toList());
        return ChildNodeList;
    }

结果

[
  {
    "id": 1,
    "name": "爷",
    "parentId": 0,
    "childNodeList": [
      {
        "id": 3,
        "name": "爷-爸",
        "parentId": 1,
        "childNodeList": [
          
            "id": 6,
            "name": "爷-爸-大儿子",
            "parentId": 3,
            "childNodeList": []
          },
          {
            "id": 7,
            "name": "爷-爸-小儿子",
            "parentId": 3,
            "childNodeList": []
          }
        ]
      },
      {
        "id": 4,
        "name": "爷-叔",
        "parentId": 1,
        "childNodeList": [
          {
            "id": 10,
            "name": "爷-叔-大儿子",
            "parentId": 4,
            "childNodeList": []
          },
          {
            "id": 11,
            "name": "爷-叔-小儿子",
            "parentId": 4,
            "childNodeList": []
          }
        ]
      }
    ]
  },
  {
    "id": 2,
    "name": "二爷",
    "parentId": 0,
    "childNodeList": [
      {
        "id": 5,
        "name": "二爷-爸",
        "parentId": 2,
        "childNodeList": [
          {
            "id": 8,
            "name": "二爷-爸-大儿子",
            "parentId": 5,
            "childNodeList": []
          },
          {
            "id": 9,
            "name": "二爷-爸-小儿子",
            "parentId": 5,
            "childNodeList": []
          }
        ]
      }
    ]
  }
]