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http://www.cnblogs.com/liuxinls/archive/2013/02/01/2888863.html

http://www.cnblogs.com/Yjianyong/archive/2010/08/05/1792976.html

http://blog.csdn.net/xiaobai1593/article/details/7065955

http://blog.csdn.net/zztoll/article/details/8694256