参考:

c++ 中 char 与 string 之间的相互转换问题
https://www.cnblogs.com/devilmaycry812839668/p/6353807.html

c++已经是字符串string了,怎么具体提取其中的某个字母
https://zhidao.baidu.com/question/388222143.html

C++ 字符串
https://www.runoob.com/cplusplus/cpp-strings.html

C++怎么从一个字符串中读取一个字符?
https://zhidao.baidu.com/question/259704265.html

C++ string substr()
https://blog.csdn.net/sunshihua12829/article/details/50484966

C++中int与string的相互转换
https://blog.csdn.net/u010510020/article/details/73799996

c++ 将一个char 转化为string
https://blog.csdn.net/carbon06/article/details/79353821

参考:

Java 中初始化 List 的五种方法
https://www.jianshu.com/p/4c8c0e78061d#:~:text=%E5%9C%A8%20Java%20%E4%B8%AD%E5%88%9D%E5%A7%8B%E5%8C%96%20List%20%E7%9A%84%E4%BA%94%E7%A7%8D%E6%96%B9%E6%B3%95%201.%E6%9E%84%E9%80%A0%20List%20%E5%90%8E%E4%BD%BF%E7%94%A8,List.add%20%E5%88%9D%E5%A7%8B%E5%8C%96%202.%E4%BD%BF%E7%94%A8%20%7B%20%7B%7D%7D%20%E5%8F%8C%E6%8B%AC%E5%8F%B7%E8%AF%AD%E6%B3%95%203.%E4%BD%BF%E7%94%A8%20Arrays.asList