如何在Java中返回樹形結構 最佳實踐

self_control發表於2014-12-17
Java

點選(此處)摺疊或開啟

  1. import java.util.ArrayList;
  2. import java.util.HashMap;
  3. import java.util.List;
  4. import java.util.Map;

  6. public class TestTree {
  7.     public static void main(String[] args) {
  8.         TestData data = new TestData();
  9.         Map<String, TreeNode> midStr = new HashMap<String, TreeNode>();
  10.         
  11.         /**把list中的資料 放到 map中，方便後續的查詢*/
  12.         for (int n = 0; n < data.listTreeNode.size(); n++) {
  13.             midStr.put(data.listTreeNode.get(n).getId(),
  14.                     data.listTreeNode.get(n));
  15.         }
  16.         
  17.         String root = null; //用來儲存根節點的id
  18.         
  19.         /*關鍵操作
  20.          * 遍歷 map 中的TreeNode 找到 父親節點，如果找不到父親節點，那這個TreeNode就是根節點。
  21.          * 把自己放到父親節點的 children 列表中
  22.          */
  23.         for (Map.Entry<String, TreeNode> entry : midStr.entrySet()) {
  24.             TreeNode t = midStr.get(entry.getValue().getParentId());
  25.             if (t != null)
  26.                 midStr.get(entry.getValue().getParentId()).getChildren()
  27.                         .add(entry.getValue());
  28.             else
  29.                 root = entry.getKey();
  30.         }
  31.         System.out.println(midStr.get(root));
  32.         TreeNode ret = midStr.get(root);
  33.         System.out.println(\"\");

  35.     }
  36. }

  38. /**
  39.  * 樹形結構
  40.  * */
  41. class TreeNode {
  42.     private String id;
  43.     private String parentId;
  44.     private List<TreeNode> children = new ArrayList<TreeNode>();;

  46.     public TreeNode(String p_id, String p_parentId) {
  47.         this.id = p_id;
  48.         this.parentId = p_parentId;
  49.     }

  51.     public String getId() {
  52.         return id;
  53.     }

  55.     public void setId(String id) {
  56.         this.id = id;
  57.     }

  59.     public String getParentId() {
  60.         return parentId;
  61.     }

  63.     public void setParentId(String parentId) {
  64.         this.parentId = parentId;
  65.     }

  67.     public List<TreeNode> getChildren() {
  68.         return children;
  69.     }

  71.     public void setChildren(List<TreeNode> children) {
  72.         this.children = children;
  73.     }

  75. }

  77. /**
  78.  * 模擬資料庫返回資料 List <DTO>
  79.  * */
  80. class TestData {
  81.     public List<TreeNode> listTreeNode = new ArrayList<TreeNode>();
  82.     TestData() {
  83.         listTreeNode.add(new TreeNode("1", "0"));

  85.         listTreeNode.add(new TreeNode("7", "3"));
  86.     
  87.         listTreeNode.add(new TreeNode("2", "1"));

  89.         listTreeNode.add(new TreeNode("3", "1"));

  91.         listTreeNode.add(new TreeNode("4", "2"));

  93.         listTreeNode.add(new TreeNode("5", "2"));

  95.         listTreeNode.add(new TreeNode("6", "1"));
  96.     }
  97. }


來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/30066956/viewspace-1371172/，如需轉載，請註明出處，否則將追究法律責任。

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