For everyone who wants to study Java introductory, I highly recommend Hongpak's lectures. They are so fun and easy to understand!!!!! + Thanks to Hongpak, the concepts I vaguely knew were now clearly understood, and the concepts I didn't know were completely organized! Other Java concept lectures were boring and there were parts I didn't understand, so it was really hard to listen, but Hongpak's lectures were so fun that I didn't realize how much time had passed. I really wish Hongpak would cover concepts like lambda expressions and threads more. Please..