(Good programming is not only the basic skill of developers, but also the watershed of ability. In addition to meeting the basic functions, how to make your code concise, efficient and reusable? In addition to constant iteration, learning design patterns is the best shortcut. Because design pattern is a summary of experience that developers use repeatedly through repeated experiments, it is also the best solution to general problems. However, many people fall into the misunderstanding that design patterns are abstract knowledge and can only be used for interviews; They learn sample code, but they can't write it themselves; The design pattern is too simple to deal with complex business problems. Remove these obstacles and make the design pattern really suit you.)