java递归获取某个父节点下面的所有子节点
package com.demo.web.test; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Objects; import com.demo.web.model.Menu; import com.google.gson.Gson; public class Test7 { private static List<Menu> treeList = new ArrayList<>(); //全局变量 public static void main(String[] args) { // List<Menu> menuList=new ArrayList<Menu>(); List<Menu> pidList=new ArrayList<Menu>(); Menu mu=new Menu(); mu.setId(1); pidList.add(mu); mu.setName("目录"); mu.setParentid("0"); Menu mu1=new Menu(); mu1.setId(2); mu1.setName("目录1"); mu1.setParentid("1"); Menu mu2=new Menu(); mu2.setId(3); mu2.setName("目录2"); mu2.setParentid("1"); Menu mu3=new Menu(); mu3.setId(4); mu3.setName("目录3"); mu3.setParentid("1"); //目录3下子节点 Menu mu4=new Menu(); mu4.setId(5); mu4.setName("目录4"); mu4.setParentid("4"); treeList.add(mu); treeList.add(mu1); treeList.add(mu2); treeList.add(mu3); treeList.add(mu4); //pid System.out.println("pidList:-------------------"+pidList); List<Menu> tree = getTree(treeList,pidList); for (Menu menu : tree) { System.out.println(menu.getId()+" ------- "+menu.getName()+" "+menu.getChildren().get(2).getChildren()); } System.out.println("7715-=-----------"+tree.get(0).getChildren()); Gson gson = new Gson();//import com.google.gson.Gson; String result = gson.toJson(tree);//pojo System.out.println("我看看0---------"+result); } public static List<Menu> getTree(List<Menu> menu,List<Menu> parentList) { //先获取到所有数据 // treeList=MenuMapper.getList(); if(menu==null) return null; //获取到所有一级节点 // List<Menu> parentList = this.MenuMapper.findParentList(); List<Menu> list = new ArrayList<>(); if(parentList != null){ for (int i = 0; i < parentList.size(); i++) { list.add(recursiveTree(parentList.get(i).getId())); } } return list; } /** * 递归算法解析成树形结构 * @param cid */ public static Menu recursiveTree(Integer cid) { Menu node = getMenuById(cid); List<Menu> childTreeNodes = getChildTreeById(cid); for(Menu child : childTreeNodes){ Menu n = recursiveTree(child.getId()); List<Menu> list = new ArrayList<Menu>(); list.add(n); System.out.println(node.getChildren()); if (node.getChildren()==null) { List<Menu> li = new ArrayList<Menu>(); node.setChildren(li); } // node.setChildren(list); node.getChildren().add(n); } return node; } /** * 根据CID查询节点对象 */ public static Menu getMenuById(Integer cid){ Map map = getTreeMap(); return (Menu) map.get(cid); } /** * 一次性取所有数据,为了减少对数据库查询操作 * @return */ public static Map getTreeMap(){ Map map = new HashMap<Integer, Menu>(); if(null != treeList){ for(Menu d : treeList){ map.put(d.getId(), d); } } return map; } /** * 根据父节点CID获取所有了节点 */ public static List<Menu> getChildTreeById(Integer cid){ List<Menu> list = new ArrayList<>(); if(null != treeList){ for (Menu d : treeList) { if(null != cid){ if (cid.equals(Integer.valueOf(d.getParentid()))) { list.add(d); } } } } return list; } }
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