java 递归处理树形结构数据

待我称王封你为后i 2022-11-14 14:46 332阅读 0赞

在实战开发中经常有树形菜单、树形目录等业务需求。在设计数据库时一般使用id<----->parentId的结构来做。本文简单介绍以递归方式处理树形数据。

package com.agileai.esb.smc.domain;
     
     
     
    import java.util.*;
     
    import net.sf.json.JSONArray;
     
    public class TreeBuilder {
     
            
     
             List<TreeBuilder.Node> nodes = new ArrayList<TreeBuilder.Node>();
     
     
     
             public TreeBuilder(List<Node> nodes) {
     
                       super();
     
                       this.nodes= nodes;
     
             }
     
            
     
             /**
              * 构建JSON树形结构
              * @return
              */
     
             public String buildJSONTree() {
     
                       List<Node> nodeTree = buildTree();
     
                       JSONArray jsonArray = JSONArray.fromObject(nodeTree);
     
                       return jsonArray.toString();
     
             }
     
            
     
             /**
              * 构建树形结构
              * @return
              */
     
             public List<Node> buildTree() {
     
                       List<Node>treeNodes = new ArrayList<Node>();
     
                       List<Node>rootNodes = getRootNodes();
     
                       for (Node rootNode : rootNodes) {
     
                                buildChildNodes(rootNode);
     
                                treeNodes.add(rootNode);
     
                       }
     
                       return treeNodes;
     
             }
     
            
     
             /**
              * 递归子节点
              * @param node
              */
     
             public void buildChildNodes(Node node) {
     
           List<Node> children = getChildNodes(node); 
     
           if (!children.isEmpty()) {
     
                for(Node child : children) {
     
                         buildChildNodes(child);
     
                } 
     
                node.setMenus(children);
     
           }
     
             }
     
     
     
             /**
              * 获取父节点下所有的子节点
              * @param nodes
              * @param pnode
              * @return
              */
     
             public List<Node> getChildNodes(Node pnode) {
     
                       List<Node>childNodes = new ArrayList<Node>();
     
                       for (Node n : nodes){
     
                                if (pnode.getId().equals(n.getPid())) {
     
                                         childNodes.add(n);
     
                                }
     
                       }
     
                       return childNodes;
     
             }
     
            
     
             /**
              * 判断是否为根节点
              * @param nodes
              * @param inNode
              * @return
              */
     
             public boolean rootNode(Node node) {
     
                       boolean isRootNode = true;
     
                       for (Node n : nodes){
     
                                if (node.getPid().equals(n.getId())) {
     
                                         isRootNode= false;
     
                                         break;
     
                                }
     
                       }
     
                       return isRootNode;
     
             }
     
            
     
             /**
              * 获取集合中所有的根节点
              * @param nodes
              * @return
              */
     
             public List<Node> getRootNodes() {
     
                       List<Node>rootNodes = new ArrayList<Node>();
     
                       for (Node n : nodes){
     
                                if (rootNode(n)) {
     
                                         rootNodes.add(n);
     
                                }
     
                       }
     
                       return rootNodes;
     
             }
     
            
     
             public static class Node {
     
                      
     
                       private String id;
     
                       private String pid;
     
                       private String text;
     
                       private String url;
     
                       private List<Node> menus;
     
                      
     
                       public Node() {}
     
     
     
                       public Node(String id, String pid, String text, String url) {
     
                                super();
     
                                this.id =id;
     
                                this.pid =pid;
     
                                this.text =text;
     
                                this.url =url;
     
                       }
     
                      
     
                       public String getId() {
     
                                return id;
     
                       }
     
                       public void setId(String id) {
     
                                this.id =id;
     
                       }
     
                       public String getPid() {
     
                                return pid;
     
                       }
     
                       public void setPid(String pid) {
     
                                this.pid =pid;
     
                       }
     
                       public String getText() {
     
                                return text;
     
                       }
     
                       public void setText(String text) {
     
                                this.text =text;
     
                       }
     
                       public String getUrl() {
     
                                return url;
     
                       }
     
                       public void setUrl(String url) {
     
                                this.url =url;
     
                       }
     
                       public List<Node> getMenus() {
     
                                return menus;
     
                       }
     
                       public void setMenus(List<Node> menus) {
     
                                this.menus= menus;
     
                       }
     
             }
     
            
     
             public static void main(String[] args) {
     
                      
     
                       List<Node>nodes = new ArrayList<Node>();
     
                       Node p1 = new Node("01", "","01", "");
     
                       Node p6 = new Node("02", "","02", "");
     
                       Node p7 = new Node("0201", "02","0201", "");
     
                       Node p2 = new Node("0101", "01","0101", "");
     
                       Node p3 = new Node("0102", "01","0102", "");
     
                       Node p4 = new Node("010101", "0101","010101", "");
     
                       Node p5 = new Node("010102", "0101","010102", "");
     
                       Node p8 = new Node("03", "","03", "");
     
                       nodes.add(p1);
     
                       nodes.add(p2);
     
                       nodes.add(p3);
     
                       nodes.add(p4);
     
                       nodes.add(p5);
     
                       nodes.add(p6);
     
                       nodes.add(p7);
                       
                       nodes.add(p8);
                      
     
                       TreeBuilder treeBuilder = new TreeBuilder(nodes);
     
                       System.out.println(treeBuilder.buildJSONTree());
     
             }
     
    }