Java递归如何正确输出树形菜单

本文实例为大家分享了java递归输出树形菜单的具体代码，供大家参考，具体内容如下

首先我们要建立树节点的类：

package com.tree; 

public class Node {
 private Integer id;
 private Integer parentId;
 private String name;
 private String link; 

 public Integer getId() {
  return id;
 }
 public void setId(Integer id) {
  this.id = id;
 }
 public Integer getParentId() {
  return parentId;
 }
 public void setParentId(Integer parentId) {
  this.parentId = parentId;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public String getLink() {
  return link;
 }
 public void setLink(String link) {
  this.link = link;
 }
} 

输出树形菜单类：

package com.tree; 

import java.util.ArrayList;
import java.util.List; 

public class Tree {
 private StringBuffer html = new StringBuffer();
 private List<Node> nodes; 

 public Tree(List<Node> nodes){
  this.nodes = nodes;
 } 

 public String buildTree(){
  html.append("<ul>");
  for (Node node : nodes) {
   Integer id = node.getId();
   if (node.getParentId() == null) {
    html.append("\r\n<li id='" + id + "'>" + node.getName()+ "</li>");
    build(node);
   }
  }
  html.append("\r\n</ul>");
  return html.toString();
 } 

 private void build(Node node){
  List<Node> children = getChildren(node);
  if (!children.isEmpty()) {
   html.append("\r\n<ul>");
   for (Node child : children) {
    Integer id = child.getId();
    html.append("\r\n<li id='" + id + "'>" + child.getName()+ "</li>");
    build(child);
   }
   html.append("\r\n</ul>");
  }
 } 

 private List<Node> getChildren(Node node){
  List<Node> children = new ArrayList<Node>();
  Integer id = node.getId();
  for (Node child : nodes) {
   if (id.equals(child.getParentId())) {
    children.add(child);
   }
  }
  return children;
 }
} 

然后我们来测试一下：

import java.util.ArrayList;
import java.util.List; 

import cn.com.tree.Node;
import cn.com.tree.Tree; 

public class Test { 

 /**
  * @param args
  */
 public static void main(String[] args) {
  List<Node> nodes = new ArrayList<Node>(); 

  Node node1 = new Node();
  node1.setId(1);
  node1.setName("node1");
  node1.setParentId(null);
  node1.setLink(null);
  nodes.add(node1); 

  Node node11 = new Node();
  node11.setId(11);
  node11.setName("node11");
  node11.setParentId(1);
  node11.setLink(null);
  nodes.add(node11); 

  Node node111 = new Node();
  node111.setId(111);
  node111.setName("node111");
  node111.setParentId(11);
  node111.setLink(null);
  nodes.add(node111); 

  Node node12 = new Node();
  node12.setId(12);
  node12.setName("node12");
  node12.setParentId(1);
  node12.setLink(null);
  nodes.add(node12); 

  Node node2 = new Node();
  node2.setId(2);
  node2.setName("node2");
  node2.setParentId(null);
  node2.setLink(null);
  nodes.add(node2); 

  Node node21 = new Node();
  node21.setId(21);
  node21.setName("node21");
  node21.setParentId(2);
  node21.setLink(null);
  nodes.add(node21); 

  Node node3 = new Node();
  node3.setId(3);
  node3.setName("node3");
  node3.setParentId(null);
  node3.setLink(null);
  nodes.add(node3); 

  Tree tree = new Tree(nodes);
  System.out.println(tree.buildTree());
 }
} 

输出的结果：

<ul>
<li id='1'>node1</li>
<ul>
<li id='11'>node11</li>
<ul>
<li id='111'>node111</li>
</ul>
<li id='12'>node12</li>
</ul>
<li id='2'>node2</li>
<ul>
<li id='21'>node21</li>
</ul>
<li id='3'>node3</li>
</ul>

浏览器效果：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。