基于JAVA8的lambda递归的treeNode树形遍历

1.TreeNode类

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.List;@Data
@NoArgsConstructor
@AllArgsConstructor
public class TreeNode {Integer id;String value;/** 子节点信息 */List<TreeNode> childrens;/** 父节点信息,根节点的父Id是0 */Integer parentId;public TreeNode(Integer id, String value, Integer parentId) {this.id = id;this.value = value;this.parentId = parentId;}
}

2.测试类

import cn.hutool.json.JSON;
import cn.hutool.json.JSONUtil;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;public class TreeNodeAssemble {public static void main(String[] args) {List<TreeNode> list = createList();//根据parentId=0获取根节点List<TreeNode> collect = list.stream().filter(m -> m.parentId == 0).map((x) -> {x.childrens = getChildren(x, list);return x;}).collect(Collectors.toList());JSON json = JSONUtil.parse(collect);System.out.println(json);}/*** 递归查询子节点* @param root* @param listAll* @return*/private static List<TreeNode> getChildren(TreeNode root, List<TreeNode> listAll) {List<TreeNode> children = listAll.stream().filter(x-> Objects.equals(x.parentId, root.id)).map(y->{y.childrens = getChildren(y,listAll);return y;}).collect(Collectors.toList());return children;}private static List<TreeNode> createList() {List<TreeNode> list = Arrays.asList(new TreeNode(1,"跟节点",0),new TreeNode(2,"韦德-狗1",1),new TreeNode(3,"韦德-猪1",1),new TreeNode(4,"韦德-狗1-2",2),new TreeNode(5,"韦德-狗1-3",2),new TreeNode(6,"韦德-猪1-2",3),new TreeNode(7,"韦德-狗1-2-4",4),new TreeNode(8,"韦德-狗1-2-5",4),new TreeNode(9,"韦德-猪2-3",6),new TreeNode(10,"韦德-猪2-4",6));return list;}}