https://juejin.im/entry/5865cff1ac502e006d5eaf4a
http://blog.csdn.net/u011007180/article/details/53384874
http://www.voidcn.com/blog/wangjun5159/article/p-6198700.html
http://www.cnblogs.com/Alight/p/3947592.html
http://www.cnblogs.com/Alight/p/5120935.html
https://www.zhihu.com/question/19719997
http://www.cnblogs.com/binbinyouni/p/6070715.html
http://www.jb51.net/article/69977.htm
