Model a Course Roster
By the end of this lesson, you'll be able to:
- Write the CourseRoster class holding a List<Student>
- Add a method to enroll a student into the roster
- Add a method to report how many students are currently enrolled
Prerequisites: "Model a Student"
Holding a list of students
public class CourseRoster {
private String courseName;
private List<Student> enrolledStudents = new List<Student>();
public CourseRoster(String courseName) {
this.courseName = courseName;
}
public void enroll(Student student) {
enrolledStudents.add(student);
}
public Integer getEnrollmentCount() {
return enrolledStudents.size();
}
}enrolledStudents starts as an empty list the moment a CourseRoster is created, and enroll() grows it one student at a time — the roster owns and protects its own list, exactly like Student protects its own fields.
Putting Student and CourseRoster together
CourseRoster apexBasics = new CourseRoster('Apex Basics');
Student alice = new Student('S001', 'Alice Nkosi', 'alice@example.com');
Student ben = new Student('S002', 'Ben Dlamini', 'ben@example.com');
apexBasics.enroll(alice);
apexBasics.enroll(ben);
System.debug(apexBasics.getEnrollmentCount()); // 2This is composition (Module 11) in action: CourseRoster has a list of Student objects rather than being one itself — the natural fit, since a roster isn't a kind of student.
Exercise
Add a method listStudentDescriptions() to CourseRoster that returns a List<String> of every enrolled student's describe() output.
Show hint
Loop over enrolledStudents, calling describe() on each, adding to a new List<String>.
Model a Course Roster Quiz
My Notes
Log in to keep private notes on this lesson.
Questions about this lesson
No questions yet — be the first to ask.
Log in to ask a question about this lesson.
Summary
CourseRoster models the second piece from the design sketch — a class that holds a growing collection of Student objects and reports on them.