compareTo()

/* Compare "this" student to "that" student (the other object) */
public int compareTo(Student that) {                                // 1
    if (this.gpa > that.gpa) {                                      // 2
        return 1;                                                   // 2
    } else if (this.gpa < that.gpa) {                               // 3
        return -1;                                                  // 3
    } else {                                                        // 4
        return 0;                                                   // 4
    }
}