auto-boxing and cache problem http://blog.csdn.net/xad707348125/article/details/47017633
swap http://www.voidcn.com/article/p-tcufudpi-vt.html
why "string" special? https://www.zhihu.com/question/31345592
原文：http://www.cnblogs.com/yumanman/p/7604798.html