섹션2 - 문자 인코딩 note : https://github.com/CodingWon/adv2/blob/master/note/%5BSec2%5D%20%EB%AC%B8%EC%9E%90%20%EC%9D%B8%EC%BD%94%EB%94%A9.md code : https://github.com/CodingWon/adv2/tree/master/workspace/java-adv2/src/sec2/charset