optional
string,int转换:
https://www.cnblogs.com/vhyc/p/7684475.html
int 和 long, int 转换 long b= a,反过来 int a = (int)b
https://www.cnblogs.com/vhyc/p/10784432.html
json
前端:https://www.cnblogs.com/vhyc/p/8434529.html
Java:https://www.cnblogs.com/vhyc/p/10439064.html
guava
https://www.cnblogs.com/vhyc/p/10669595.html
apacha.common.util
https://www.cnblogs.com/vhyc/p/10666116.html