使用MAP实现管理学生和班级，可以新添加一个或几个学生到某个班级， 从某班级删除一个或几个学生， 查询某个班级的所有女生， 查询年龄大于20岁的所有学生-Use MAP realization management students and class, can add new one or several students to a class, from a class deletes one or several students, inquires the class all girl