Clean Code

Listing B-1 (continued)
SerialDate.Java

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358
Appendix B: 
org.jfree.date.SerialDate
537 
538 /**
539 * Returns the number of the last day of the month, taking into account 
540 * leap years.
541 *
542 * @param month the month.
543 * @param yyyy the year (in the range 1900 to 9999).
544 *
545 * @return the number of the last day of the month.
546 */
547 public static int lastDayOfMonth(final int month, final int yyyy) {
548 
549 final int result = LAST_DAY_OF_MONTH[month];
550 if (month != FEBRUARY) {
551 return result;
552 }
553 else if (isLeapYear(yyyy)) {
554 return result + 1;
555 }
556 else {
557 return result;
558 }
559 
560 }
561 
562 /**
563 * Creates a new date by adding the specified number of days to the base 
564 * date.
565 *
566 * @param days the number of days to add (can be negative).
567 * @param base the base date.
568 *
569 * @return a new date.
570 */
571 public static SerialDate addDays(final int days, final SerialDate base) {
572 
573 final int serialDayNumber = base.toSerial() + days;
574 return SerialDate.createInstance(serialDayNumber);
575 
576 }
577 
578 /**
579 * Creates a new date by adding the specified number of months to the base 
580 * date.
581 *
582 * If the base date is close to the end of the month, the day on the result
583 * may be adjusted slightly: 31 May + 1 month = 30 June.
584 *
585 * @param months the number of months to add (can be negative).
586 * @param base the base date.
587 *
588 * @return a new date.
589 */
590 public static SerialDate addMonths(final int months, 
591 final SerialDate base) {
592 
593 final int yy = (12 * base.getYYYY() + base.getMonth() + months - 1) 
594 / 12;
595 final int mm = (12 * base.getYYYY() + base.getMonth() + months - 1) 
596 % 12 + 1;
597 final int dd = Math.min(
598 base.getDayOfMonth(), SerialDate.lastDayOfMonth(mm, yy)