Java（七）synchronized详解

http://zhangjunhd.blog.51cto.com/113473/70300/

http://blog.youkuaiyun.com/chenguang79/article/details/677720

http://www.cnblogs.com/devinzhang/archive/2011/12/14/2287675.html

http://www.cnblogs.com/GnagWang/archive/2011/02/27/1966606.html