What is this repo?

This is a place where I learn Java features and some of its best practices

Which book am I following?

Effective Java 2/E, 2nd Edition, Joshua Bloch
Java의 정석, 3rd Edition, 남궁성

Which JDK am I using

JDK 21 (JDK 21.0.3) However, the books I am reading are based on Java 8 (or 1.8)