将无序的List数据转成树形结构数据

你的名字 2022-05-09 01:10 251阅读 0赞

# 将无序的List数据转成树形结构数据 #

在平常的项目中，经常会用到树形结构数据，看了一些网友写的生成树形结构的方法，感觉基本都会把层级写的比较死，所以在这里写一个不关联层级的生成方式（层级信息在生成树的时候赋值），依靠code和parentCode两个信息生成最终的树。

### Tree.java ###

package patterns.structure.composite; import java.util.ArrayList; import java.util.List; import java.util.stream.Collectors; /** * 用组合模式构建一棵树 * * @author joker * @date 2018-09-27 22:47 */ public class Tree { private String code; private String name; private String parentCode; private Integer level; private Tree parent; private List<Tree> node; public Tree() { } public Tree(String code, String name, String parentCode, Integer level) { this.code = code; this.name = name; this.parentCode = parentCode; this.level = level; } public String getCode() { return code; } public void setCode(String code) { this.code = code; } /** * 将一组无序的树组装成树形结构的数据 * * @param treeList * @return */ public static List<Tree> buildTree(List<Tree> treeList) { if (treeList == null || treeList.size() == 0) { return null; } List<Tree> trees = getRootNode(treeList); trees.forEach(node -> node.setLevel(0)); List<Tree> parentNodes = trees; List<Tree> subNodes; int level = 1; do { treeList.removeAll(parentNodes); subNodes = getRootNode(treeList); if (subNodes != null && subNodes.size() > 0) { for (Tree subNode : subNodes) { subNode.setLevel(level); for (Tree parentNode : parentNodes) { if (codeEquals(parentNode.getCode(), subNode.getParentCode())) { List<Tree> list = parentNode.getNode(); if (list == null) { list = new ArrayList<>(); parentNode.setNode(list); } list.add(subNode); subNode.setParent(parentNode); } } } } parentNodes = subNodes; level++; } while (subNodes != null); return trees; } /** * 获取treeList中的顶级节点 * * @param treeList * @return */ public static List<Tree> getRootNode(List<Tree> treeList) { if (treeList == null || treeList.size() == 0) { return null; } List<String> codes = treeList.stream().map(tree -> tree.getCode()).collect(Collectors.toList()); List<Tree> trees = treeList.stream().filter( node -> !codes.contains(node.getParentCode()) || codeEquals(node.getCode(), node.getParentCode())) .collect(Collectors.toList()); return trees; } /** * 判断两个编码是否相同 * * @param code * @param parentCode * @return */ public static boolean codeEquals(String code, String parentCode) { if (code == null) { if (parentCode == null) { return true; } } else { if (parentCode != null && code.equals(parentCode)) { return true; } } return false; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getParentCode() { return parentCode; } public void setParentCode(String parentCode) { this.parentCode = parentCode; } public Integer getLevel() { return level; } public void setLevel(Integer level) { this.level = level; } public Tree getParent() { return parent; } public void setParent(Tree parent) { this.parent = parent; } public List<Tree> getNode() { return node; } public void setNode(List<Tree> node) { this.node = node; } @Override public String toString() { return "Tree{" + "code='" + code + '\'' + ", name='" + name + '\'' + ", parentCode='" + parentCode + '\'' + ", level=" + level + '}'; } }

### TreeTest.java ###

package patterns.structure.composite; import java.util.ArrayList; import java.util.List; /** * @author joker * @date 2018-09-28 22:20 */ public class TreeTest { public static void main(String[] args) { Tree tree0 = new Tree(null,"根节点",null,null); Tree tree1 = new Tree("1","根节点",null,null); Tree tree2 = new Tree("2","根节点",null,null); Tree tree3 = new Tree("3","根节点","2",null); Tree tree4 = new Tree("4","根节点","2",null); Tree tree5 = new Tree("5","根节点","0",null); Tree tree6 = new Tree("6","根节点","0",null); Tree tree7 = new Tree("7","根节点","6",null); Tree tree8 = new Tree("8","根节点","7",null); Tree tree9 = new Tree("9","根节点","5",null); Tree tree10 = new Tree("10","根节点","5",null); Tree tree11 = new Tree("11","根节点","13",null); Tree tree12 = new Tree("12","根节点","13",null); Tree tree13 = new Tree("13","根节点","10",null); List<Tree> treeList = new ArrayList<>(); treeList.add(tree0); treeList.add(tree1); treeList.add(tree2); treeList.add(tree3); treeList.add(tree4); treeList.add(tree5); treeList.add(tree6); treeList.add(tree7); treeList.add(tree8); treeList.add(tree9); treeList.add(tree10); treeList.add(tree11); treeList.add(tree12); treeList.add(tree13); List<Tree> trees = Tree.buildTree(treeList); printTree(trees); } private static void printTree(List<Tree> trees){ for(Tree tree : trees){ String prefix = "----"; for(int i=0;i<tree.getLevel();i++){ prefix += "----"; } System.out.println(prefix+tree); if(tree.getNode() != null && tree.getNode().size() > 0){ printTree(tree.getNode()); } } } }

\#\#\#运行结果

> \----Tree\{code=‘null’, name=‘根节点’, parentCode=‘null’, level=0\}  
> \--------Tree\{code=‘1’, name=‘根节点’, parentCode=‘null’, level=1\}  
> \--------Tree\{code=‘2’, name=‘根节点’, parentCode=‘null’, level=1\}  
> \------------Tree\{code=‘3’, name=‘根节点’, parentCode=‘2’, level=2\}  
> \------------Tree\{code=‘4’, name=‘根节点’, parentCode=‘2’, level=2\}  
> \----Tree\{code=‘5’, name=‘根节点’, parentCode=‘0’, level=0\}  
> \--------Tree\{code=‘9’, name=‘根节点’, parentCode=‘5’, level=1\}  
> \--------Tree\{code=‘10’, name=‘根节点’, parentCode=‘5’, level=1\}  
> \------------Tree\{code=‘13’, name=‘根节点’, parentCode=‘10’, level=2\}  
> \----------------Tree\{code=‘11’, name=‘根节点’, parentCode=‘13’, level=3\}  
> \----------------Tree\{code=‘12’, name=‘根节点’, parentCode=‘13’, level=3\}  
> \----Tree\{code=‘6’, name=‘根节点’, parentCode=‘0’, level=0\}  
> \--------Tree\{code=‘7’, name=‘根节点’, parentCode=‘6’, level=1\}  
> \------------Tree\{code=‘8’, name=‘根节点’, parentCode=‘7’, level=2\}

个人github代码地址  
[https://github.com/jokerChen1991/pattern/blob/master/src/com/jokerchen/pattern/structure/composite/][https_github.com_jokerChen1991_pattern_blob_master_src_com_jokerchen_pattern_structure_composite]

个人原创，转载请注明 [https://blog.csdn.net/Joker\_2007/article/details/82894857][https_blog.csdn.net_Joker_2007_article_details_82894857]

[https_github.com_jokerChen1991_pattern_blob_master_src_com_jokerchen_pattern_structure_composite]: https://github.com/jokerChen1991/pattern/blob/master/src/com/jokerchen/pattern/structure/composite/
[https_blog.csdn.net_Joker_2007_article_details_82894857]: https://blog.csdn.net/Joker_2007/article/details/82894857