Even though I don't know much about the collection framework, I thought it would be easy since I've used it once or twice, but I realized once again that there is no end to learning 😊😊 As with the previous lectures, this lecture was also very good with detailed explanations and examples. In particular, the last practice problem required a lot of thought compared to the other problems, but I felt a great sense of accomplishment when I solved it on my own. (It also gave me a chance to review the enumeration that I had almost forgotten 😊😊) Thank you for your always sincere lectures!!