SWE 619 In Class Exercise Number 0

Instructions: Work with your assigned group. You might decide to change groups later, but for today, stick with this group.

Your group should spend a few minutes getting acquainted. Explain a bit about yourself: full-time student?, working in software development?, why are you taking this class?, etc.
Decide on a mechanism for group communication. Google docs? Discord? Something else?

Now address a technical topic. This exercise touches on some of the thorny issues in data abstraction and inheritance. There is a lot going on in this example. Hence don't worry if it seems confusing today. We'll revisit this example several times over the course of the semester.

Consider the following (textbook) code:

public class User {
    private String name;
    public User (String name) { this.name = name; }
    @Override public boolean equals (Object obj) {
       if (!(obj instanceof User)) return false;
       return ((User) obj).name.equals(this.name);
    }
    // other methods omitted
}
public class SpecialUser extends User {
    private int id;
    public SpecialUser (String name, int id) { super(name); this.id = id; }
    @Override public boolean equals (Object obj) {
       if (!(obj instanceof SpecialUser)) return false;
       return super.equals(obj) && ((SpecialUser) obj).id == this.id;
    }
    // other methods omitted
}

Walk though the execution of the equals() method in class User for a few well-chosen (pairs of) objects. What happens at each point in the execution?
What does it mean for an equals() implementation to be correct? How do you know? Be as concrete as you can.
Is the given implementation of equals() in class User correct? Again, be concrete. If there is a problem, find a specific object (test case!) that demonstrates the problem.

Note: These next two questions are much harder.
How does inheritance complicate the correctness discussion for equals() in class SpecialUser?
What is your assessment of the equals() method in the SpecialUser class?