6. Factory pattern

http://arnakiel.blogspot.kr/2010/01/%EB%94%94%EC%9E%90%EC%9D%B8-%ED%8C%A8%ED%84%B4%EC%9D%98-%EB%84%A4%EB%B2%88%EC%A7%B8-%ED%8C%A9%ED%86%A0%EB%A6%AC-%ED%8C%A8%ED%84%B4factory-pattern-1.html

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