Thank you very much. I really feel that to become a proper developer, you need to have a solid foundation, persistence on key points, and not fall behind Younghan's son. (Even a 12-year-old can develop like this and not give up, so I think I should keep going.) The intermediate Java PDF is 400 pages long and needs to be polished, so Younghan, take care of your health and let's all work hard and create even a small program.