public int compare(Record a, Record b) {
        if (a == null && b == null) {
            return 0;
        } else if ((a == null && b != null)
                || (a != null && b == null)) {
            return a == null ? 1 : -1;
        } else {
            int recordCompare = 0;
            if (a.zipcode > b.zipcode) {
                recordCompare = 1;
            } else if (a.zipcode < b.zipcode) {
                recordCompare = -1;
            }

            return recordCompare;
        }
    }