Clean Code

Listing B-1 (continued)
SerialDate.Java

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359
Appendix B: 
org.jfree.date.SerialDate
599 );
600 return SerialDate.createInstance(dd, mm, yy);
601 
602 }
603 
604 /**
605 * Creates a new date by adding the specified number of years to the base 
606 * date.
607 *
608 * @param years the number of years to add (can be negative).
609 * @param base the base date.
610 *
611 * @return A new date.
612 */
613 public static SerialDate addYears(final int years, final SerialDate base) {
614 
615 final int baseY = base.getYYYY();
616 final int baseM = base.getMonth();
617 final int baseD = base.getDayOfMonth();
618 
619 final int targetY = baseY + years;
620 final int targetD = Math.min(
621 baseD, SerialDate.lastDayOfMonth(baseM, targetY)
622 );
623 
624 return SerialDate.createInstance(targetD, baseM, targetY);
625 
626 }
627 
628 /**
629 * Returns the latest date that falls on the specified day-of-the-week and 
630 * is BEFORE the base date.
631 *
632 * @param targetWeekday a code for the target day-of-the-week.
633 * @param base the base date.
634 *
635 * @return the latest date that falls on the specified day-of-the-week and 
636 * is BEFORE the base date.
637 */
638 public static SerialDate getPreviousDayOfWeek(final int targetWeekday, 
639 final SerialDate base) {
640 
641 // check arguments...
642 if (!SerialDate.isValidWeekdayCode(targetWeekday)) {
643 throw new IllegalArgumentException(
644 "Invalid day-of-the-week code."
645 );
646 }
647 
648 // find the date...
649 final int adjust;
650 final int baseDOW = base.getDayOfWeek();
651 if (baseDOW > targetWeekday) {
652 adjust = Math.min(0, targetWeekday - baseDOW);
653 }
654 else {
655 adjust = -7 + Math.max(0, targetWeekday - baseDOW);
656 }
657 
658 return SerialDate.addDays(adjust, base);
659 
660 }