定义一个实体

package com.tdy.tiger.trr;

import lombok.Data;

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

@Data
public class Menu {

    private Integer id;//id

    private Integer pid;//父id

    private String name;//名称



    List<Menu> child = new ArrayList<>();//子类

    public Menu(Integer id,Integer pid, String name) {
        this.id = id;
        this.name = name;
        this.pid = pid;
    }
}

实现方法

package com.tdy.tiger.trr;

import com.alibaba.fastjson.JSON;

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

public class MenuTraversal {

    public static void main(String[] args) {
//虚拟点假数据
        Menu rootMenu = new Menu(0, -1, "根");
        List<Menu> children = new ArrayList<>();
        children.add(new Menu(1, 0, "资产"));
        children.add(new Menu(2, 0, "监控"));
        children.add(new Menu(3, 0, "系统管理"));

        children.add(new Menu(4, 1, "机房"));
        children.add(new Menu(5, 1, "机柜"));
        children.add(new Menu(6, 1, "主机"));

        children.add(new Menu(7, 2, "趋势图"));
        children.add(new Menu(8, 2, "最新数据"));

        children.add(new Menu(9, 3, "用户管理"));
        children.add(new Menu(10, 3, "角色管理"));
        children.add(new Menu(11, 3, "菜单管理"));

//        rootMenu.child = children;

        System.out.println(rootMenu);

        findChildMenu(rootMenu, children);

        System.out.println(JSON.toJSONString(rootMenu));


    }

    private static void findChildMenu(Menu parentMenu, List<Menu> menus) {

        menus.forEach(menu -> {
            if (parentMenu.getId() == menu.getPid()) {
                parentMenu.child.add(menu);
                findChildMenu(menu, menus);
            }
        });
    }
}