https://velog.io/@blessole/Java-CHAR-0-%EC%9D%B4-%EB%AD%98%EA%B9%8C-char-%EB%AC%B8%EC%9E%90%EB%A5%BC-%EC%88%AB%EC%9E%90%EB%A1%9C-%EB%B3%80%ED%99%98%ED%95%98%EB%8A%94-%EB%B0%A9%EB%B2%95
