public void addnewcourse(course cours, Student st1, Student st2, Student st3)
{//at least course must have 3 studnts , so manager add this three
// and afterthat he can add more by addstudent method
course co = cours;
co.addstudent(st1);
co.addstudent(st2);
co.addstudent(st3);
}
public void addstudent_to_existcourse(Student st, course co)
{
co.addstudent(st);
}