列表(list)和树(tree)相互转换

跟前端交互时 经常会有树或者列表的转换

import com.alibaba.fastjson.JSON;
import lombok.Data;
import org.assertj.core.util.Lists;
import org.junit.Test;
import org.springframework.util.CollectionUtils;
import org.springframework.util.ObjectUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;


public class TreeToListTest {
    
    

    @Data
    class TreeNode {
    
    
        private String nodeId;
        private String nodeName;
        private String parentId;
        List<TreeNode> childrenNode;

        public TreeNode() {
    
    
        }

        public TreeNode(String nodeId, String nodeName, String parentId) {
    
    
            this.nodeId = nodeId;
            this.nodeName = nodeName;
            this.parentId = parentId;
        }

    }

    public void treeToList(List<TreeNode> treeNodes, List<TreeNode> listNode, String parentId) {
    
    
        treeNodes.forEach(node -> {
    
    
            TreeNode treeNode = new TreeNode();
            treeNode.setNodeId(node.getNodeId());
            treeNode.setNodeName(node.getNodeName());
            treeNode.setParentId(parentId);
            listNode.add(treeNode);
            if (!ObjectUtils.isEmpty(node.getChildrenNode())) {
    
    
                treeToList(node.getChildrenNode(), listNode, node.getNodeId());
            }
        });
    }

    private void ListToTree(List<TreeNode> listNode, List<TreeNode> treeNode) {
    
    
        if (CollectionUtils.isEmpty(treeNode)) {
    
    
            return;
        }
        treeNode.forEach(tNode->{
    
    
            List<TreeNode> collect = listNode.stream().filter(nodeTemp -> tNode.getNodeId().equals(nodeTemp.getParentId())).collect(Collectors.toList());
            tNode.setChildrenNode(collect);
            listNode.removeAll(collect);
            ListToTree(listNode,collect);
        });
    }


    @Test
    public void demo() {
    
    
        List<TreeNode> listNode = new ArrayList<>();
        listNode.add(new TreeNode("1", "1", "0"));
        listNode.add(new TreeNode("2", "1", "1"));
        listNode.add(new TreeNode("3", "1", "1"));
        listNode.add(new TreeNode("4", "1", "2"));
        listNode.add(new TreeNode("5", "1", "3"));
        listNode.add(new TreeNode("6", "1", "2"));
        listNode.add(new TreeNode("7", "1", "3"));
        ArrayList<TreeNode> treeNodes = Lists.newArrayList(new TreeNode("0", "1", null));
        ListToTree(listNode, treeNodes);
        System.out.println("转化成树是: "+JSON.toJSONString(treeNodes));

        ArrayList<TreeNode> listNodes = Lists.newArrayList();
        treeToList(treeNodes,listNodes,null);
        System.out.println("转化列表:  "+JSON.toJSONString(listNodes));
    }


}