Been using Kotlin for 3, 4 yrs now. I recently took “Kotlin for Java Developers” on Coursera, and it was very interesting and there were a lot to learn. Wonder if there are more courses like this. I’m looking for a course for more experienced user, because the Coursera course took me 2 days to complete it. (and although I learned a lot there were lots of things I already knew.) Or a book like effective java of java. Any recommendations are welcome! Thanks.