Thank you for helping me become a better developer. I am still reading the hardcover edition of 'Toby's Spring 3.0'. When I first read it, I skipped over chapters 1 to 8 and only looked at the practical parts. However, as time passed, I ended up looking at the first part, chapters 1 to 8, again. The lecture focused on the first part, and explained the principles while excluding the difficult parts of Spring implementation as much as possible. Toby's unique build-up method of explaining the principles was still effective. Here are some things I didn't feel through the book, but I felt through the lecture: - The need to separate codes according to the reason and timing of change - A good habit of Opening and Closing at the same time when writing code that requires resource release - How to use IntelliSense with camel case in IntelliJ IDEA - How to use the TimeUnit class to conveniently use Thread.sleep - How to reduce dependencies by separating packages based on DIP (Dependency Inversion Principle) - How to control the environment using Clock.fixed - Double bracket technique that can be conveniently used when configuring Spring Configuration In fact, the things I learned listed above are additional parts, and while watching the lecture, I kept thinking about 'how to create a structure that is easy to maintain'. These parts were not completely resolved even after watching the lecture, but since it gave me some direction, I will think harder in the future. Thank you. Lastly, I felt that the condition was different for each lecture. Stay healthy. Once again, thank you for helping me become a better developer.