2.设计一个简单的课程管理系统（CourseManager）。主要功能包括：

(1)课程信息的录入。主要包括：课程号（no）、课程名（name）、学分（grade）等；

(2)课程信息的查询。根据课程号、课程名和学分等查询课程的信息。注意：查询结果可能不唯一。

(3)课程信息的修改。根据课程号查询到指定课程的信息，再用新的内容替换。

(4)课程信息的删除。根据课程号删除指定课程的信息。

设计时，采用层次化设计法，将类分为界面层（ui）、功能层（business）和持久层（persistence）3层，放在不同子包中。整个系统的代码放在exe4_2包中。-2. Design a simple course management system (CourseManager). Key features include:

(1) entry program information. Including: course number (no), course name (name), credits (grade) and the like

(2) information about courses. Information based curriculum, course name and credit and other inquiries courses. Note: query results may not be unique.

(3) Course modify information. Inquiry based curriculum to the specified courses, and then replaced with new content.

(4) Delete course information. Remove a specified course of information based curriculum.

Design, the use of hierarchical design method, the class is divided into the interface layer (ui), the functional layer (business) and persistence (persistence) 3 layers in different sub-packages. The system code in the exe4_2 package.