(It involves not only the code, but also the thinking of design and the misunderstanding of security. In this course, each class is a core focus of Java business development. Each knowledge point corresponds to 2 ~ 5 cases, and each case is explained according to "knowledge introduction - > restore business scenario - > error implementation - > correct implementation - > principle analysis - > small summary", which not only helps you avoid the common pit of this knowledge point, but also allows you to know the root cause of the pit and improve your technical ability. These contents can not only help you write better code, but also help you further complement your knowledge network and increase your confidence in the interview. You can even use these cases as checklists for code review to help other projects avoid pitfalls and help the team grow together.)