public interface RegistrationI {

  /**
   * Read students.txt and populate the students TreeMap.
   */
  public void readStudents();

  /**
   * Read in courses.txt and populate the courses TreeMap.
   */
  public void readCourses();

  /**
   * Look up a Student object from a student id.
   */
  public StudentI getStudent(int studentId);

  /**
   * Look up a Course object from a courseId.
   */
  public CourseI getCourse(String courseId);

  /**
   * If the student is registered for the course, provide the date
   * of registration. If the student is not registered, return null.
   */
  public java.util.Date checkRegistration(int studentId, String courseId);

  /**
   * Register the student for the course. If there's a problem, throw a
   * RegException. See instructions.
   */
  public void addRegistration(int studentId, String courseId) throws RegException;
}