最新最基础的项目，对用户，账单，供应商进行增删改查等各类操作，能够清晰的展示用JDBC操作数据库(The latest and most basic projects, such as users, bills, suppliers, additions, deletions, and other operations, can clearly display the JDBC operating database.)

实现登录、账单、销售功能，以及超级管理员的修改密码(Implement login, bill, sales function)

楼主基础比较差，第一次写这些东西，写的比较差 多多包涵(The first time I uploaded it, I wrote it rather poorly.)