UML Diagram: Reflexive Association with class instance clarification

Question

I used a plug-in in Eclipse Neon which is called ObjectAid, it's a plug-in that generates a UML Diagram automatically.

Now I understand everything in the generated UML except for one thing, which is the label next to the arrow "~class instance". What does that part mean? UML Diagram

This is just an identical image, not the real one, of the UML generated so please understand that that's just an example.

EDIT:

//more codes here
static APAGenerator generateAPA = new APAGenerator();

public static void main(String[] args) {
    try {
        generateAPA.run();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
//more codes here

If you want a more precise answer, it could help that's you post the code of Class and the generated schema. — granier
As @Kilian said, the name of the role is strange and the package visibilty is not often used. Do you really declare a package visibility ? — granier
@granier, I already sorted it out and I'm no longer looking for an answer, thanks for the concern. Though for this part " Do you really declare a package visibility ?", no, I didn't specify any access modifier for the class instance I created. I've provided a code snippet above for the class instance. — Helquin

qwerty_so qwerty_so · Accepted Answer · 2017-11-12T16:06:32

Well, I can't speak for this ObjectAid (and what their makers thought they should do), but as per UML specification the ~ tells the visibility is package and it's followed by the role name which the association takes (IOW: the attribute being used). So the name is class instance which seems odd.

UML Diagram: Reflexive Association with class instance clarification

2 Answers