UML: how to implement Association class in Java

Question

I have this UML Association class. Note that: horizontal line is a solid line and the vertical line is a dashed line.

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Answer 1

First of all, don't use Vector, as it's an old class that shouldn't be used anymore for more than 10 years. Use either a Set or a List.

If the Transcript class contains information about the way a student attends a course (for example, the date of its subscription to the course), you could implement it like this:

class Student {
    Set transcripts;
}

class Transcript {
    Student student;
    Course course;
    Date subscriptionDate;
}

class Course {
    Set transcripts;
}

That doesn't prevent you from providing a method in Student that returns all his courses: 

public Set getCourses() {
    Set result = new HashSet();
    for (Transcript transcript : transcripts) {
        result.add(transcript.getCourse());
    }
    return result;
}

If Transcript doesn't contain any information, then it's probably there to model how these classes would be mapped in database tables, where the only way to have a many-to-many association between two tables is to use a join table holding the IDs of the two associated tables.