Java将List数据转换为树形结构

import com.fasterxml.jackson.annotation.JsonInclude;

import java.util.List;


public class Menu {

    private String menuCode;

    private String menuName;

    private String parentMenuCode;

    private String parentMenuName;

    @JsonInclude(JsonInclude.Include.NON_NULL)
    private List childrenMenu;

    public String getMenuCode() {
        return menuCode;
    }

    public void setMenuCode(String menuCode) {
        this.menuCode = menuCode;
    }

    public String getMenuName() {
        return menuName;
    }

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

    public String getParentMenuCode() {
        return parentMenuCode;
    }

    public void setParentMenuCode(String parentMenuCode) {
        this.parentMenuCode = parentMenuCode;
    }

    public String getParentMenuName() {
        return parentMenuName;
    }

    public void setParentMenuName(String parentMenuName) {
        this.parentMenuName = parentMenuName;
    }

    public List getChildrenMenu() {
        return childrenMenu;
    }

    public void setChildrenMenu(List childrenMenu) {
        this.childrenMenu = childrenMenu;
    }

    @Override
    public String toString() {
        return "Menu{" +
                "menuCode='" + menuCode + ''' +
                ", menuName='" + menuName + ''' +
                ", parentMenuCode='" + parentMenuCode + ''' +
                ", parentMenuName='" + parentMenuName + ''' +
                ", childrenMenu=" + childrenMenu +
                '}';
    }
}

import com.alibaba.fastjson.JSONObject;
import com.demo.service.pojo.Menu;
import org.apache.commons.lang.StringUtils;
import org.springframework.util.CollectionUtils;

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


public class TestDemo {

    public static void main(String[] args) {
        List menuList = new ArrayList<>();
        Menu m1 = new Menu();
        m1.setParentMenuCode("0");
        m1.setParentMenuName("根菜单");
        m1.setMenuCode("01");
        m1.setMenuName("角色管理");

        Menu m2 = new Menu();
        m2.setParentMenuCode("01");
        m2.setParentMenuName("角色管理");
        m2.setMenuCode("0101");
        m2.setMenuName("角色添加");

        Menu m3 = new Menu();
        m3.setParentMenuCode("01");
        m3.setParentMenuName("角色管理");
        m3.setMenuCode("0102");
        m3.setMenuName("角色删除");

        Menu m4 = new Menu();
        m4.setParentMenuCode("0");
        m4.setParentMenuName("根菜单");
        m4.setMenuCode("02");
        m4.setMenuName("权限管理");

        menuList.add(m1);
        menuList.add(m2);
        menuList.add(m3);
        menuList.add(m4);

        System.out.println("转换前：" + JSONObject.toJSONString(menuList));

        menuList = handleMenu(menuList, "0");

        System.out.println("转换后：" + JSONObject.toJSONString(menuList));
    }

    public static List handleMenu(List menuList, String rootMenuCode) {
        if(CollectionUtils.isEmpty(menuList)) {
            return new ArrayList<>();
        }
        List menus = new ArrayList<>();

        for (Menu menu : menuList) {
            if (StringUtils.equals(menu.getParentMenuCode(), rootMenuCode)) {
                menus.add(getChildMenu(menu, menuList));
            }
        }

        return menus;
    }

    public static Menu getChildMenu(Menu menu, List menuList) {
        for (Menu m : menuList) {
            if(StringUtils.equals(m.getParentMenuCode(), menu.getMenuCode())) {
                if(null == menu.getChildrenMenu()) {
                    menu.setChildrenMenu(new ArrayList<>());
                }
                menu.getChildrenMenu().add(getChildMenu(m, menuList));
            }
        }
        return menu;
    }
}