java list 转树 tree 的三种写法

List对象数组转为tree

代码是自己写的，今天学习来的。下一步，写成工具类。

pom里面加上：阿里的fastjson


<dependency>
<groupId>net.sf.json-lib</groupId>
<artifactId>json-lib</artifactId>
<version>2.4</version>
</dependency>

import com.alibaba.fastjson.JSON;
import java.util.ArrayList;
import java.util.List;
/**
* <p></p>
*
* @package: com.tree
* @class: TreeNode1
* @date: 2018/3/27
* @author: jcroad(caoyajing @ yunmel.com)
* @since 1.0
*/
public class TreeNode {
private Integer id;
private Integer pid;
private String name;
private List<TreeNode> children;
TreeNode(Integer id, Integer pid, String name) {
this.id = id;
this.pid = pid;
this.name = name;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getPid() {
return pid;
}
public void setPid(Integer pid) {
this.pid = pid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<TreeNode> getChildren() {
return children;
}
public void setChildren(List<TreeNode> children) {
this.children = children;
}
public static void main(String[] args) {
List<TreeNode> list = new ArrayList<TreeNode>();
list.add(new TreeNode(1, 0, "1"));
list.add(new TreeNode(2, 0, "2"));
list.add(new TreeNode(3, 2, "3"));
list.add(new TreeNode(4, 3, "4"));
list.add(new TreeNode(5, 4, "5"));
list.add(new TreeNode(6, 5, "6"));
List<TreeNode> treeList = new ArrayList<TreeNode>();
List<TreeNode> treeList1 = new ArrayList<TreeNode>();
List<TreeNode> treeList2 = new ArrayList<TreeNode>();
List<TreeNode> treeList3 = new ArrayList<TreeNode>();
//方法一、
treeList = listGetStree(list);
treeList1 = listToTree(list);
treeList2 = toTree(list);
System.out.println(JSON.toJSONString(treeList));
System.out.println(JSON.toJSONString(treeList1));
System.out.println(JSON.toJSONString(treeList2));
}
private static List<TreeNode> listGetStree(List<TreeNode> list) {
List<TreeNode> treeList = new ArrayList<TreeNode>();
for (TreeNode tree : list) {
//找到根
if (tree.getPid() == 0) {
treeList.add(tree);
}
//找到子
for (TreeNode treeNode : list) {
if (treeNode.getPid() == tree.getId()) {
if (tree.getChildren() == null) {
tree.setChildren(new ArrayList<TreeNode>());
}
tree.getChildren().add(treeNode);
}
}
}
return treeList;
}
/**
* 方法二、
* @param list
* @return
*/
public static List<TreeNode> listToTree(List<TreeNode> list) {
//用递归找子。
List<TreeNode> treeList = new ArrayList<TreeNode>();
for (TreeNode tree : list) {
if (tree.getPid() == 0) {
treeList.add(findChildren(tree, list));
}
}
return treeList;
}
private static TreeNode findChildren(TreeNode tree, List<TreeNode> list) {
for (TreeNode node : list) {
if (node.getPid() == tree.getId()) {
if (tree.getChildren() == null) {
tree.setChildren(new ArrayList<TreeNode>());
}
tree.getChildren().add(findChildren(node, list));
}
}
return tree;
}
/**
*方法三
* @param list
* @return
*/
private static List<TreeNode> toTree(List<TreeNode> list) {
List<TreeNode> treeList = new ArrayList<TreeNode>();
for (TreeNode tree : list) {
if(tree.getPid() == 0){
treeList.add(tree);
}
}
for (TreeNode tree : list) {
toTreeChildren(treeList,tree);
}
return treeList;
}
private static void toTreeChildren(List<TreeNode> treeList, TreeNode tree) {
for (TreeNode node : treeList) {
if(tree.getPid() == node.getId()){
if(node.getChildren() == null){
node.setChildren(new ArrayList<TreeNode>());
}
node.getChildren().add(tree);
}
if(node.getChildren() != null){
toTreeChildren(node.getChildren(),tree);
}
}
}
}

java list 转树 tree 的三种写法

java list 转树 tree 的三种写法

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