read

http://farsight2011.blog.sohu.com/269919651.html

http://www.baidu.com/s?wd=java%E5%AE%9E%E4%BE%8B%E5%8C%96%E5%AF%B9%E8%B1%A1&rsv_spt=1&issp=1&f=8&rsv_bp=0&rsv_idx=2&ie=utf-8&tn=baiduhome_pg&bs=java%20new

http://www.zhihu.com/question/20314377