java使用stream遍历树结构

@Test
public void testtree(){
//模拟从数据库查询出来
List

menus = Arrays.asList(
new Menu(1,“根节点”,0),
new Menu(2,“子节点1”,1),
new Menu(3,“子节点1.1”,2),
new Menu(4,“子节点1.2”,2),
new Menu(5,“根节点1.3”,2),
new Menu(6,“根节点2”,1),
new Menu(7,“根节点2.1”,6),
new Menu(8,“根节点2.2”,6),
new Menu(9,“根节点2.2.1”,7),
new Menu(10,“根节点2.2.2”,7),
new Menu(11,“根节点3”,1),
new Menu(12,“根节点3.1”,11)
);

    //获取父节点
    List collect = menus.stream().filter(m -> m.getParentId() == 0).map(
            (m) -> {
                m.setChildList(getChildrens(m, menus));
                return m;
            }
    ).collect(Collectors.toList());
    System.out.println("-------转json输出结果-------");
    System.out.println(JSON.toJSON(collect));
}

/**
 * 递归查询子节点
 * @param root  根节点
 * @param all   所有节点
 * @return 根节点信息
 */
private List getChildrens(Menu root, List all) {
    List children = all.stream().filter(m -> {
        return Objects.equals(m.getParentId(), root.getId());
    }).map(
            (m) -> {
                m.setChildList(getChildrens(m, all));
                return m;
            }
    ).collect(Collectors.toList());
    return children;
}

@Data
@Builder
public class Menu {
/**
* id
/
public Integer id;
/*
* 名称
/
public String name;
/*
* 父id ，根节点为0
/
public Integer parentId;
/*
* 子节点信息
*/
public List

childList;

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

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

}