阿里云缓存pdf： https://library-cdq.oss-cn-beijing.aliyuncs.com/technology/PlantUML.pdf
状态图
https://www.cnblogs.com/jingwhale/p/4230235.html
https://baike.baidu.com/item/状态图/4925373?fr=aladdin
状态机
https://baike.baidu.com/item/状态机/6548513?fr=aladdin
https://blog.csdn.net/benjonc/article/details/79870947
类图
https://www.cnblogs.com/warmsmile/p/11449197.html
https://www.cnblogs.com/xdyixia/p/9265214.html
https://www.cnblogs.com/Percy_Lee/articles/9633445.html
