1. Runtime.getRuntime().freeMemory() 和 jvisualvm.exe

http://blog.csdn.net/u011004037/article/details/45740673

2.jmap命令

http://www.cnblogs.com/o-andy-o/archive/2013/06/11/3132335.html

3.mat工具

http://www.open-open.com/lib/view/open1404350384858.html