http://www.cnblogs.com/wangchenyang/archive/2011/08/23/2150530.html
http://www.blogjava.net/weishuangshuang/archive/2011/11/08/363237.html
http://www.cnblogs.com/jiugehuanying/archive/2012/01/12/2320058.html
原文：http://www.cnblogs.com/daishuguang/p/4033265.html