2017/02
[Design Pattern] Null Object Pattern
http://dsmoon.tistory.com/entry/NULL-OBJECT-%ED%8C%A8%ED%84%B4http://sjava.net/2009/09/null-object-pattern/http://blog.seulgi.kim/2015/09/null-object-pattern.htmlhttp://changsuk.me/?p=2036
http://dsmoon.tistory.com/entry/NULL-OBJECT-%ED%8C%A8%ED%84%B4http://sjava.net/2009/09/null-object-pattern/http://blog.seulgi.kim/2015/09/null-object-pattern.htmlhttp://changsuk.me/?p=2036