• Java递归树(构建和收集子孙节点二种方式)

    Java递归树(构建和收集子孙节点二种方式)

    TreeUtil

    1.递归工具类:(构建递归树 且支持 通过 buildByRecursive方法 depth参数控制递归的层级深度 )

    /**
 * @Description: 树节点
 * @Author: 徐刘
 * @Date: 2020/12/5 12:18
 */
@Data
public class TreeNode {

    <span class="token keyword">protected</span> String id<span class="token punctuation">;</span>

<span class="token keyword">protected</span> String parentId<span class="token punctuation">;</span>

<span class="token keyword">private</span>  <span class="token keyword">int</span> level<span class="token punctuation">;</span>
<span class="token comment">// 是否有子节点</span>
<span class="token keyword">private</span>  <span class="token keyword">boolean</span> isLeaf<span class="token punctuation">;</span>

List<span class="token generics function"><span class="token punctuation">&lt;</span>TreeNode<span class="token punctuation">&gt;</span></span> children <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token operator">&lt;</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">add</span><span class="token punctuation">(</span>TreeNode node<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
    children<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

    

    }
    

    /**
    

      

    • 

      @Description: tree结构工具类
      

      • 

    • 

      @Author: 徐刘
      

      • 

    • 

      @Date: 2020/12/5 12:17
      
/
      
public class TreeUtil {
      
/      *
      

        

      • 

        两层循环实现建树
        

        • 

      • 

      • 

        @param treeNodes 传入的树节点列表
        

        • 

      • 

        @return
        
*/
        
public static <T extends TreeNode> List<T> bulid(List<T> treeNodes, Object root) {
        

        List<T> trees = new ArrayList<T>();
        

        for (T treeNode : treeNodes) {
        

         <span class="token keyword">if</span> <span class="token punctuation">(</span>root<span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span>treeNode<span class="token punctuation">.</span><span class="token function">getParentId</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
     trees<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>treeNode<span class="token punctuation">)</span><span class="token punctuation">;</span>
 <span class="token punctuation">}</span>

 <span class="token keyword">for</span> <span class="token punctuation">(</span>T it <span class="token operator">:</span> treeNodes<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
     <span class="token keyword">if</span> <span class="token punctuation">(</span>StringUtils<span class="token punctuation">.</span><span class="token function">equalsIgnoreCase</span><span class="token punctuation">(</span>it<span class="token punctuation">.</span><span class="token function">getParentId</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> treeNode<span class="token punctuation">.</span><span class="token function">getId</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
         <span class="token keyword">if</span> <span class="token punctuation">(</span>CollectionUtils<span class="token punctuation">.</span><span class="token function">isEmpty</span><span class="token punctuation">(</span>treeNode<span class="token punctuation">.</span><span class="token function">getChildren</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
             treeNode<span class="token punctuation">.</span><span class="token function">setChildren</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token operator">&lt;</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token punctuation">}</span>
         treeNode<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>it<span class="token punctuation">)</span><span class="token punctuation">;</span>
     <span class="token punctuation">}</span>
 <span class="token punctuation">}</span>

        

        }
        
return trees;
        
}
        

        • 

      

      /**
      

        

      • 

        使用递归方法建树
        

        • 

      • 

      • 

        @param treeNodes
        

        • 

      • 

        @param depth 需要递归的层级 深度
        

        • 

      • 

        @return
        
*/
        
public static <T extends TreeNode> List<T> buildByRecursive(List<T> treeNodes, Object root, Integer depth) {
        

        List<T> trees = new ArrayList<T>();
        
int level = 1;
        
for (T treeNode : treeNodes) {
        
// 获取根节点(可以有多个根节点)
        
if (root.equals(treeNode.getParentId())) {
        
//     每个根节点递归添加子节点
        
trees.add(findChildren(treeNode, treeNodes,level,depth));
        
treeNode.setLevel(level);
        
}
        
}
        
return trees;
        
}
        

        • 

      

      /**
      

        

      • @Description: 递归查找子节点
        • 

      • @Author: 徐刘
        • 

      • @Date: 2020/12/7 9:57
        • 

      • @param treeNode
        • 

      • @param treeNodes
        • 

      • @param level 层级
        • 

      • @param depth
        • 

      • @Return: T
        
*/
        
public static <T extends TreeNode> T findChildren(T treeNode, List<T> treeNodes, int level, Integer depth) {
        
if(depthnull){
        
depth = Integer.MAX_VALUE;
        
}
        
for (T it : treeNodes) {
        
if (StringUtils.equalsIgnoreCase(treeNode.getId(), it.getParentId())) {
        
if (treeNode.getChildren()  null) {
        
treeNode.setChildren(new ArrayList<>());
        
}
        
// 控制递归的 层级深度
        
if(level>=depth){
        
return treeNode;
        
}
        
treeNode.add(findChildren(it, treeNodes, level +1, depth));
        
}
        
treeNode.setLevel(level);
        
treeNode.setLeaf(treeNode.getChildren().size() <= 0);
        
}
        
return treeNode;
        
}
        • 

      

      • 

    

    }
    

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    1. 递归构建 非树形结构 ,返回指定节点 下子孙节点 收集成一个list 集合

      商品分类 示例

       /**
	 * @desc 递归查找出该节点下面的子孙节点
	 * @return
	 * @author xuliu
	 * @date 2020/7/4 15:32
	 */

    <span class="token keyword">public</span> List<span class="token generics function"><span class="token punctuation">&lt;</span>CPProductClass<span class="token punctuation">&gt;</span></span> <span class="token function">buildByRecursive</span><span class="token punctuation">(</span>List<span class="token generics function"><span class="token punctuation">&lt;</span>CPProductClass<span class="token punctuation">&gt;</span></span> targetProductClasslist<span class="token punctuation">,</span> String classid<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	List<span class="token generics function"><span class="token punctuation">&lt;</span>CPProductClass<span class="token punctuation">&gt;</span></span> trees <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token operator">&lt;</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	Integer level <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
	<span class="token function">findChildren</span><span class="token punctuation">(</span>trees<span class="token punctuation">,</span>targetProductClasslist<span class="token punctuation">,</span>classid<span class="token punctuation">,</span>level<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token keyword">return</span> trees<span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token keyword">private</span> List<span class="token generics function"><span class="token punctuation">&lt;</span>CPProductClass<span class="token punctuation">&gt;</span></span> <span class="token function">findChildren</span><span class="token punctuation">(</span>List<span class="token generics function"><span class="token punctuation">&lt;</span>CPProductClass<span class="token punctuation">&gt;</span></span> trees<span class="token punctuation">,</span> List<span class="token generics function"><span class="token punctuation">&lt;</span>CPProductClass<span class="token punctuation">&gt;</span></span> targetProductClasslist<span class="token punctuation">,</span> String classid<span class="token punctuation">,</span>Integer level<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	<span class="token keyword">if</span><span class="token punctuation">(</span>targetProductClasslist <span class="token operator">!=</span>null <span class="token operator">&amp;&amp;</span> targetProductClasslist<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">&gt;</span><span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
		<span class="token keyword">for</span> <span class="token punctuation">(</span>CPProductClass cpProductClass <span class="token operator">:</span> targetProductClasslist<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
			<span class="token keyword">if</span> <span class="token punctuation">(</span>cpProductClass<span class="token punctuation">.</span><span class="token function">getParentclassid</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span>classid<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
				<span class="token function">findChildren</span><span class="token punctuation">(</span>trees<span class="token punctuation">,</span>targetProductClasslist<span class="token punctuation">,</span>cpProductClass<span class="token punctuation">.</span><span class="token function">getClassid</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span>level<span class="token operator">+</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
				cpProductClass<span class="token punctuation">.</span><span class="token function">setClasslevel</span><span class="token punctuation">(</span>level<span class="token punctuation">)</span><span class="token punctuation">;</span>
				trees<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>cpProductClass<span class="token punctuation">)</span><span class="token punctuation">;</span>
			<span class="token punctuation">}</span>
		<span class="token punctuation">}</span>
	<span class="token punctuation">}</span>
	<span class="token keyword">return</span> trees<span class="token punctuation">;</span>
<span class="token punctuation">}</span>

    

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    https://blog.csdn.net/weixin_43298522/article/details/118057675
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  • 原文地址：https://www.cnblogs.com/sunny3158/p/16692600.html
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