参考链接：
- https://www.cnblogs.com/kevin-top/archive/2010/07/07/1772660.html
- https://www.cnblogs.com/because/archive/2011/04/04/2005178.html
- http://blog.sina.com.cn/s/blog_8388ce730100s4k6.html
- https://blog.csdn.net/LuYuling_666/article/details/104701109
- https://blog.csdn.net/xuwei296/article/details/8548121
- https://www.cnblogs.com/neuhawk/archive/2006/09/28/517507.html
- https://bbs.csdn.net/topics/310116954
- https://bbs.csdn.net/topics/100161670
- https://www.cnblogs.com/shenchao/p/4064444.html
- https://www.cnblogs.com/gongcheng97/p/4362251.html
- http://www.360doc.com/content/12/1219/22/10939365_255183523.shtml