谈谈Runtime类中的freeMemory,totalMemory,maxMemory等几个方法

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