树有关

例子：https://www.cnblogs.com/kubixuesheng/p/4391381.html
https://blog.youkuaiyun.com/weixin_42914296/article/details/81563707
https://www.cnblogs.com/Dylansuns/p/6791270.html
https://docs.microsoft.com/zh-cn/dotnet/api/system.windows.forms.treenode?redirectedfrom=MSDN&view=netframework-4.8
http://www.cnblogs.com/goodyao/archive/2008/09/18/1293364.html
https://bbs.youkuaiyun.com/topics/270045319
https://www.cnblogs.com/duanrantao/p/9359137.html
https://bbs.youkuaiyun.com/wap/topics/60113187
https://www.jianshu.com/p/cd6813739cd2
https://blog.youkuaiyun.com/qq_31617121/article/details/79691636
https://blog.youkuaiyun.com/coder__666/article/details/80349039
https://blog.youkuaiyun.com/presidentpresident/article/details/7549170
https://www.cnblogs.com/web424/p/6911892.html
https://blog.youkuaiyun.com/styshoo/article/details/52865386
https://blog.youkuaiyun.com/z69183787/article/details/20770645?locationNum=1
https://blog.youkuaiyun.com/baidu_35813686/article/details/82863596
https://blog.youkuaiyun.com/joker_2007/article/details/82894857
https://blog.youkuaiyun.com/qq_28165595/article/details/76836788
https://blog.youkuaiyun.com/perry0528/article/details/82527739
https://www.cnblogs.com/fthjane/p/4746186.html
MySQL教程之concat以及group_concat的用法：
https://baijiahao.baidu.com/s?id=1595349117525189591&wfr=spider&for=pc
Java有关List的stream基本操作：JAVA8 Stream接口流式方法 map操作 filter操作以及flatMap操作
https://www.cnblogs.com/xumBlog/p/9507936.html
https://blog.youkuaiyun.com/limingcai168/article/details/85265089
https://zhidao.baidu.com/question/1309066314041620539.html
https://blog.youkuaiyun.com/justloveyou_/article/details/79562574
Java 集合系列05之 LinkedList详细介绍(源码解析)和使用示例：
https://www.cnblogs.com/skywang12345/p/3308807.html#a4