https://blog.wongcw.com/2018/12/14/%e4%b8%80%e4%b8%aa%e5%91%bd%e4%bb%a4%e5%b0%b1%e8%83%bd%e6%90%ad%e5%bb%ba%e5%a5%bd%e7%9a%84java%e5%bc%80%e6%ba%90%e5%8d%9a%e5%ae%a2%e7%b3%bb%e7%bb%9f-solo/