Sort a List of objects by multiple fields [duplicate]

Answer 1

Yes, you absolutely can do this. For example:

public class PersonComparator implements Comparator
{
    public int compare(Person p1, Person p2)
    {
        // Assume no nulls, and simple ordinal comparisons

        // First by campus - stop if this gives a result.
        int campusResult = p1.getCampus().compareTo(p2.getCampus());
        if (campusResult != 0)
        {
            return campusResult;
        }

        // Next by faculty
        int facultyResult = p1.getFaculty().compareTo(p2.getFaculty());
        if (facultyResult != 0)
        {
            return facultyResult;
        }

        // Finally by building
        return p1.getBuilding().compareTo(p2.getBuilding());
    }
}

Basically you're saying, "If I can tell which one comes first just by looking at the campus (before they come from different campuses, and the campus is the most important field) then I'll just return that result. Otherwise, I'll continue on to compare faculties. Again, stop if that's enough to tell them apart. Otherwise, (if the campus and faculty are the same for both people) just use the result of comparing them by building."