JAVA API
https://docs.oracle.com/en/java/javase/16/docs/api/index.html
여러가지 참고 레퍼런스
http://www.devkuma.com/
http://tcpschool.com/java/intro
둥님 추천링크
https://jeong-pro.tistory.com/228
https://sia-code.tistory.com/37
https://mirinae312.github.io/develop/2018/06/04/jvm_gc.html
https://jins-dev.tistory.com/entry/Session-%EA%B8%B0%EB%B0%98-%EC%9D%B8%EC%A6%9D%EA%B3%BC-Token-%EA%B8%B0%EB%B0%98-%EC%9D%B8%EC%A6%9D
-일급컬렉션**
https://jojoldu.tistory.com/412
-check uncheked exception
https://umbum.dev/896
깃플로우
https://duzi077.tistory.com/270
https://velog.io/@cos/Github%EC%97%90%EC%84%9C-%ED%98%91%EC%97%85%ED%95%98%EB%8A%94-%EB%B0%A9%EB%B2%95#-git-flow