http://7sunet.iteye.com/blog/285007
http://crunchify.com/java-runtime-get-free-used-and-total-memory-in-java/
http://stackoverflow.com/questions/3571203/what-is-the-exact-meaning-of-runtime-getruntime-totalmemory-and-freememory
谈谈Runtime类中的freeMemory,totalMemory,maxMemory等几个方法
原文：http://www.cnblogs.com/diyunpeng/p/4299936.html