Easterpublic class Easter extends Object | Easter - compute the day on which Easter falls.
In the Christian religion, Easter is possibly the most important holiday
of the year, so getting its date just so is worthwhile. |
| Methods Summary |
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| public static final java.util.Calendar | findHolyDay(int year)
if (year <= 1582) {
throw new IllegalArgumentException("Algorithm invalid before April 1583");
}
int golden, century, x, z, d, epact, n;
golden = (year % 19) + 1; /* E1: metonic cycle */
century = (year / 100) + 1; /* E2: e.g. 1984 was in 20th C */
x = (3*century/4) - 12; /* E3: leap year correction */
z = ((8*century+5) / 25) -5; /* E3: sync with moon's orbit */
d = (5*year/4) - x - 10;
epact = (11*golden + 20 + z - x) % 30; /* E5: epact */
if ((epact == 25 && golden > 11) || epact == 24)
epact++;
n = 44 - epact;
n += 30 * (n < 21?1:0); /* E6: */
n += 7 - ((d+n)%7);
if (n>31) /* E7: */
return new GregorianCalendar(year, 4-1, n-31); /* April */
else
return new GregorianCalendar(year, 3-1, n); /* March */
| | public static void | main(java.lang.String[] argv)Main program, when used as a standalone application
if (argv.length == 0) {
int thisYear = new GregorianCalendar().get(Calendar.YEAR);
Calendar c = Easter.findHolyDay(thisYear);
System.out.println( c.getTime());
} else for (int i=0; i<argv.length; i++) {
int year = 0;
try {
year = Integer.parseInt(argv[i]);
System.out.println(Easter.findHolyDay(year).getTime());
} catch (IllegalArgumentException e) {
System.err.println("Year " + argv[i] + " invalid (" + e.getMessage() + ").");
}
}
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