作用
提供一个通用的树组件模型,用于将元素列表转成树节点。
实现
元素节点定义
public interface TreeNodeElement {
/**
* 当前节点key
*/
String getKey();
/**
* 父节点key
*/
String getParentKey();
}
树节点定义
package com.wangtao.springboot3.common;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonUnwrapped;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.stream.Collectors;
public class TreeNode<T extends TreeNodeElement> {
/**
* 将元素中的属性展开到当前节点中
*/
@JsonUnwrapped
private final T element;
@JsonIgnore
private TreeNode<T> parent;
private final List<TreeNode<T>> children;
private TreeNode(T element) {
this.element = element;
this.children = new ArrayList<>();
}
public void addChild(TreeNode<T> child) {
this.children.add(child);
}
public void addChildren(List<TreeNode<T>> children) {
this.children.addAll(children);
}
public void setChildren(List<TreeNode<T>> children) {
Objects.requireNonNull(children, "children must not be null!");
this.children.clear();
this.children.addAll(children);
}
public List<TreeNode<T>> getChildren() {
return Collections.unmodifiableList(this.children);
}
public T getElement() {
return element;
}
public void setParent(TreeNode<T> parent) {
this.parent = parent;
}
public TreeNode<T> getParent() {
return parent;
}
public static <T extends TreeNodeElement> TreeNode<T> of(T element) {
return new TreeNode<>(element);
}
/**
* 构建树
* O(n)时间复杂度
* @param elements 元素列表
* @return 树节点列表
*/
public static <T extends TreeNodeElement> List<TreeNode<T>> build(List<T> elements) {
Objects.requireNonNull(elements, "elements must not be null!");
List<TreeNode<T>> treeNodes = new ArrayList<>();
Map<String, TreeNode<T>> treeNodeMap = elements.stream()
.collect(Collectors.toMap(TreeNodeElement::getKey, TreeNode::of));
for (T element : elements) {
TreeNode<T> self = treeNodeMap.get(element.getKey());
TreeNode<T> parent = treeNodeMap.get(element.getParentKey());
if (Objects.nonNull(parent)) {
self.setParent(parent);
parent.addChild(self);
} else {
// 顶级节点
treeNodes.add(self);
}
}
return treeNodes;
}
public static <T extends TreeNodeElement> List<TreeNode<T>> buildByRecursion(List<T> elements) {
return buildByRecursion(elements, null);
}
/**
* 递归构建树(不推荐,时间复杂度高)
*/
public static <T extends TreeNodeElement> List<TreeNode<T>> buildByRecursion(List<T> elements, String parentKey) {
Objects.requireNonNull(elements, "elements must not be null!");
List<TreeNode<T>> treeNodes = new ArrayList<>();
for (T element : elements) {
if (Objects.equals(element.getParentKey(), parentKey)) {
TreeNode<T> treeNode = TreeNode.of(element);
List<TreeNode<T>> children = buildByRecursion(elements, element.getKey());
treeNode.addChildren(children);
treeNodes.add(treeNode);
}
}
return treeNodes;
}
}
标签:elements,TreeNode,实现,List,children,组件,element,public
From: https://www.cnblogs.com/wt20/p/18280571