http://java.sun.com/developer/technicalArticles/J2SE/mxbeans/index.html
http://jiangnanguying.iteye.com/blog/539697
http://doc.java.sun.com/DocWeb/api/all/java.lang.management.MemoryPoolMXBean
http://java.sun.com/developer/technicalArticles/J2SE/mxbeans/index.html