使用递归操作将父子关系数据转成树形结构对象

前端需要树形结构的json数据，故此 写demo记录下，方便下次查阅。

package tree;

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

/**
 * @ClassName Menu
 * @Description: TODO
 * @Author yuanqingtao
 * @Date 2020/11/19
 * @Version
 **/
public class Menu {

    private Integer id;
    private Integer parentId;//父id
    private String name;//名称
    private List<Menu> children;//子集

    public Menu() {
    }

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

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getParentId() {
        return parentId;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<Menu> getChildren() {
        return children;
    }

    public void setChildren(List<Menu> children) {
        this.children = children;
    }

    @Override
    public String toString() {
        return "{" +
                "id:" + id +
                ", parentId:" + parentId +
                ", name:'" + name + '\'' +
                ", children:" + children +
                '}';
    }

    public Menu generateTree(Integer id, List<Menu> list) {
        Menu root = new Menu();
        //查询根
        for (Menu menu : list) {
            if (menu.getId() == id) {
                root = menu;
            }
        }
        //查询子集
        List<Menu> childList = new ArrayList<>();
        for (Menu node : list) {
            if (node.getParentId() == root.getId()) {
                childList.add(node);
            }
        }
        //子集查询子集
        if (childList != null && childList.size() > 0) {
            for (Menu child : childList) {
                Menu childRoot = generateTree(child.getId(), list);
                if (root.getChildren() == null) {
                    root.setChildren(new ArrayList<>());
                }
                root.getChildren().add(childRoot);
            }
        }
        return root;
    }

    public static void main(String[] args) {
        List<Menu> list=new ArrayList<>();
        list.add(new Menu(1,0,"上海公司"));
        list.add(new Menu(2,1,"二级上海分公司"));
        list.add(new Menu(3,2,"三级上海分公司"));
        list.add(new Menu(4,1,"二级上海代理公司"));
        list.add(new Menu(5,4,"三级上海代理公司"));
        list.add(new Menu(6,5,"四级上海代理公司"));

        Menu treeJson=new Menu().generateTree(1,list);

        System.out.println(treeJson.toString());
    }


}

运行结果：{id:1, parentId:0, name:'上海公司', children:[{id:2, parentId:1, name:'二级上海分公司', children:[{id:3, parentId:2, name:'三级上海分公司', children:null}]}, {id:4, parentId:1, name:'二级上海代理公司', children:[{id:5, parentId:4, name:'三级上海代理公司', children:[{id:6, parentId:5, name:'四级上海代理公司', children:null}]}]}]}

json格式化查看结果：