Clutch release example

Question

input code:

public interface Course {

    /**
     * returns the number of units (hours) a specific course is
     */
    public int units();

    /**
     * returns the number of students signed up for the course
     */
    public int numOfStudents();

    /**
     * returns the maximum number of students the course can have signed up to it
     */
    public int maxNumStudents();

    /**
     * returns whether or not the student is enrolled in the course
     */
    public boolean registered(Student s);

    /**
     * enrolls s in the course
     * 
     * @pre     this.registered(s) == false
     * @pre     this.numOfStudents() < this.maxNumStudents()
     * 
     * @post    this.registered(s) == true
     * @post    this.numOfStudents() == $prev(this.numOfStudents()) + 1
     */
    public void register(Student s);

}


public interface Student {

    /**
     * enrolls the student in course c
     * 
     * @pre     c.registered(this) == false
     * @pre     c.numOfStudents() < c.maxNumStudents()
     * @pre     this.totalUnits() + c.units() <= 10
     * 
     * @post    c.registered(s) == true
     * @post    this.totalUnits() == $prev(this.totalUnits()) + c.units()
     */
    public void register(Course c);

    /**
     * return the total number of units this student currently is enrolled in
     * 
     * @pre     true
     * @post    0 <= $ret <= 10
     */
    public int totalUnits();

}

in the example code im trying to describe two separate objects (interfaces / classes / all), which, on the one hand, should be (I would like, at least) loosely coupled, but, on the other hand, depend on each other and require certain knowledge of each other.

in the above scenario, I need a third class that actually integrates them into a working system. its ugly, because at the moment the above definition is as weakly connected as it can be - student.register (c) changes only the student object, and course.register (s) changes only the course object. therefore, the concatenating class must run both s.register (c) and c.register (s).

although if I reinstall the entire register () logic into one class, then I will bind them tightly.

?

Answer 1

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