java 实现递归实现tree

package app.util;

import java.util.ArrayList;
import java.util.List;

import com.alibaba.fastjson.JSON;


public class Menu {
        private Integer pid;
        private String menuName;
        private Integer parentId;
        private Integer position;
        private List<Menu> childMenu;

        

 

        public Integer getPid() {
            return pid;
        }



        public void setPid(Integer pid) {
            this.pid = pid;
        }



        public String getMenuName() {
            return menuName;
        }



        public void setMenuName(String menuName) {
            this.menuName = menuName;
        }



        public Integer getParentId() {
            return parentId;
        }



        public void setParentId(Integer parentId) {
            this.parentId = parentId;
        }



        public Integer getPosition() {
            return position;
        }



        public void setPosition(Integer position) {
            this.position = position;
        }



        public List<Menu> getChildMenu() {
            return childMenu;
        }



        public void setChildMenu(List<Menu> childMenu) {
            this.childMenu = childMenu;
        }



        public Menu(Integer parentId,String menuName, Integer pid, Integer position) {
            super();
            this.parentId = parentId;
            this.menuName = menuName;
            this.pid = pid;
            this.position = position;
        }

 

        public Menu() {
            super();
        }

 


        public static void main(String[] args) {
            
            List<Menu> list=new ArrayList<Menu>();
            Menu menu1=new Menu(1, "父级1", 0, 1);
            Menu menu2=new Menu(2, "父级2", 0, 2);
            Menu menu1_1=new Menu(3, "子级1_1", 1, 1);
            Menu menu1_2=new Menu(4, "子级1_2", 1, 2);
            Menu menu1_2_1=new Menu(5, "子级1_2_1", 4, 2);
            Menu menu1_2_2=new Menu(6, "子级1_2_2", 2, 2);
            list.add(menu1);
            list.add(menu2);
            list.add(menu1_1);
            list.add(menu1_2);
            list.add(menu1_2_1);
            list.add(menu1_2_2);
            
            List<Menu> listTree=buildTree(list,0);
            
            String trssJson=JSON.toJSONString(listTree);
            System.out.println(trssJson);
        
        }
        
        public static List<Menu> buildTree(List<Menu> list,int pid){
            List<Menu> menus=new ArrayList<Menu>();
            for (Menu menu : list) { 
            
                int parentId = menu.getPid();
                int  menuId= menu.getParentId();
                if (pid == parentId) { 
                List<Menu> menuLists = buildTree(list, menuId); 
                
                menu.setChildMenu(menuLists);
                menus.add(menu); 
            } 
        } 
        
        return menus;
        }
}

成型

[
    {
        "childMenu": [
            {
                "childMenu": [
                    
                ],
                "menuName": "子级1_1",
                "parentId": 3,
                "pid": 1,
                "position": 1
            },
            {
                "childMenu": [
                    {
                        "childMenu": [
                            
                        ],
                        "menuName": "子级1_2_1",
                        "parentId": 5,
                        "pid": 4,
                        "position": 2
                    }
                ],
                "menuName": "子级1_2",
                "parentId": 4,
                "pid": 1,
                "position": 2
            }
        ],
        "menuName": "父级1",
        "parentId": 1,
        "pid": 0,
        "position": 1
    },
    {
        "childMenu": [
            {
                "childMenu": [
                    
                ],
                "menuName": "子级1_2_2",
                "parentId": 6,
                "pid": 2,
                "position": 2
            }
        ],
        "menuName": "父级2",
        "parentId": 2,
        "pid": 0,
        "position": 2
    }
]