| 1 | package net.sourceforge.calendardate; |
| 2 | import java.util.Calendar; |
| 3 | import java.util.GregorianCalendar; |
| 4 | |
| 5 | import junit.framework.TestCase; |
| 6 | |
| 7 | |
| 8 | public class ManualCalculationTestCase extends TestCase { |
| 9 | |
| 10 | |
| 11 | public void testDaysUntil() { |
| 12 | GregorianCalendar startDate = new GregorianCalendar(2000, 0, 1); |
| 13 | for (int day = -(366 * 400); day < (366 * 400); day++) { |
| 14 | GregorianCalendar endDate = new GregorianCalendar(2000, 0, 1 + day); |
| 15 | assertEquals(endDate.getTime().toString(), day, DayCounter.daysUntil(startDate, endDate)); |
| 16 | } |
| 17 | } |
| 18 | |
| 19 | |
| 20 | } |
| 21 | |
| 22 | class DayCounter { |
| 23 | public static int daysUntil(Calendar fromDate, Calendar toDate) { |
| 24 | return daysSinceEpoch(toDate) - daysSinceEpoch(fromDate); |
| 25 | } |
| 26 | |
| 27 | public static int daysSinceEpoch(Calendar day) { |
| 28 | int year = day.get(Calendar.YEAR); |
| 29 | int month = day.get(Calendar.MONTH); |
| 30 | int daysThisYear = cumulDaysToMonth[month] + day.get(Calendar.DAY_OF_MONTH) - 1; |
| 31 | if ((month > 1) && isLeapYear(year)) { |
| 32 | daysThisYear++; |
| 33 | } |
| 34 | |
| 35 | return daysToYear(year) + daysThisYear; |
| 36 | } |
| 37 | |
| 38 | public static boolean isLeapYear(int year) { |
| 39 | return (year % 400 == 0) || ((year % 100 != 0) && (year % 4 == 0)); |
| 40 | } |
| 41 | |
| 42 | static int daysToYear(int year) { |
| 43 | return (365 * year) + numLeapsToYear(year); |
| 44 | } |
| 45 | |
| 46 | static int numLeapsToYear(int year) { |
| 47 | int num4y = (year - 1) / 4; |
| 48 | int num100y = (year - 1) / 100; |
| 49 | int num400y = (year - 1) / 400; |
| 50 | return num4y - num100y + num400y; |
| 51 | } |
| 52 | |
| 53 | private static final int[] cumulDaysToMonth = { 0, 31, 59, 90, 120, 151, |
| 54 | 181, 212, 243, 273, 304, 334 }; |
| 55 | } |