java TreeUtil菜单递归工具类

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;
  }
}

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;
  }
}