Thank you so much for the great lecture!! The book Effective Java is always included in the recommended development books, so I tried to read it every time, but I gave up because it was so difficult. Thanks to Instructor Baek Gi-seon's lecture, I can understand the contents of the book. ㅠㅠ There were so many good points, but if I had to pick one, it would be that the book explained the contents concisely in theory in detail from a practical perspective. In the 'Item 3. Summary 1 - How to use constructors 1' part, regarding the part in the book that says 'it becomes difficult to test', you explained in detail using code how this method is inefficient from a certain perspective, which was really helpful to me!