If there is no database, the library management system can output the interface as println on the console. If there is no database, you can output the interface as println on the console. The complication is that if you use javaWeb, you will write the interface into the browser. First, you will create four classes, namely users, books and categories. The intermediate class consists of the first three specified categories, which are used to display, create these classes, assign values and then put them into the list collection on the interface. Adding, deleting, modifying and querying are operations on list sets.