下面递归树菜单效率低:
package com.admin.manager.storeService.util; import com.admin.manager.storeService.entity.Menu; import java.util.ArrayList; import java.util.List; /** * @author m * @date 2019/12/16 */ public class TreeUtil { /** * 获取菜单树 * @param menus 所有菜单 * @return */ public static List<Menu> menuTree(List<Menu> menus) { //返回的菜单树 List<Menu> rootMenus = new ArrayList<>(); for (Menu menu : menus) { //pid(上级Id)为0的是根菜单 if ("0".equals(menu.getPid())) { rootMenus.add(menu); } } //遍历,找到二级菜单(根菜单的id和所有菜单中的pid比较) for (Menu rootMenu : rootMenus) { List<Menu> child = getChild(String.valueOf(rootMenu.getId()), menus); rootMenu.setChildren(child); } return rootMenus; } /** * 递归获取下级菜单 * @param pid 上级Id * @param menus 所有菜单 * @return */ public static List<Menu> getChild(String pid, List<Menu> menus) { //子菜单列表 List<Menu> childList = new ArrayList<>(); for (Menu menu : menus) { if (pid.equals(menu.getPid())) { childList.add(menu); } } //遍历 递归获取子菜单的子菜单 for (Menu menu : childList) { List<Menu> child = getChild(String.valueOf(menu.getId()), menus); menu.setChildren(child); } //递归出口 childList长度为0 if (childList.size() == 0) { return new ArrayList<>(); } return childList; } }
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这个效率高点:
import com.energy.service.vo.RegionTree; import java.util.ArrayList; import java.util.Iterator; import java.util.List; /** * @author m * @date 2020/4/2 */ public class TreeUtil { /** * 创建树结构 * @param regionTrees * @return */ private List<RegionTree> tree(List<RegionTree> regionTrees) { //返回的节点树 List<RegionTree> rootNodes = new ArrayList<>(); Iterator<RegionTree> it = regionTrees.iterator(); while (it.hasNext()) { RegionTree next = it.next(); //parent(上级Id)为0的是根节点 if ("0".equals(next.getParentId())) { rootNodes.add(next); it.remove(); } } //遍历,找到二级节点 for (RegionTree regionTree : rootNodes) { List<RegionTree> child = getChild(regionTrees, regionTree.getId().toString()); regionTree.setChildren(child); } return rootNodes; } /** * 查子节点 * * @param regions * @param parentId * @return */ private List<RegionTree> getChild(List<RegionTree> regions, String parentId) { //子节点列表 List<RegionTree> childList = new ArrayList<>(); Iterator<RegionTree> it = regions.iterator(); while (it.hasNext()) { RegionTree regionTree = it.next(); if (parentId.equals(regionTree.getParentId())) { childList.add(regionTree); it.remove(); } } //遍历 递归获取子节点的子节点 for (RegionTree regionTree : childList) { List<RegionTree> child = getChild(regions, regionTree.getId().toString()); regionTree.setChildren(child); } //递归出口 childList长度为0 if (childList.size() == 0) { return new ArrayList<>(); } return childList; } }
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