org.joda.time.chrono.CopticChronology Maven / Gradle / Ivy
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/*
* Copyright 2001-2009 Stephen Colebourne
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.joda.time.chrono;
import java.util.HashMap;
import java.util.Map;
import org.joda.time.Chronology;
import org.joda.time.DateTime;
import org.joda.time.DateTimeConstants;
import org.joda.time.DateTimeField;
import org.joda.time.DateTimeZone;
import org.joda.time.field.SkipDateTimeField;
/**
* Implements the Coptic calendar system, which defines every fourth year as
* leap, much like the Julian calendar. The year is broken down into 12 months,
* each 30 days in length. An extra period at the end of the year is either 5
* or 6 days in length. In this implementation, it is considered a 13th month.
*
* Year 1 in the Coptic calendar began on August 29, 284 CE (Julian), thus
* Coptic years do not begin at the same time as Julian years. This chronology
* is not proleptic, as it does not allow dates before the first Coptic year.
*
* This implementation defines a day as midnight to midnight exactly as per
* the ISO chronology. Some references indicate that a coptic day starts at
* sunset on the previous ISO day, but this has not been confirmed and is not
* implemented.
*
* CopticChronology is thread-safe and immutable.
*
* @see Wikipedia
* @see JulianChronology
*
* @author Brian S O'Neill
* @since 1.0
*/
public final class CopticChronology extends BasicFixedMonthChronology {
/** Serialization lock */
private static final long serialVersionUID = -5972804258688333942L;
/**
* Constant value for 'Anno Martyrum' or 'Era of the Martyrs', equivalent
* to the value returned for AD/CE.
*/
public static final int AM = DateTimeConstants.CE;
/** A singleton era field. */
private static final DateTimeField ERA_FIELD = new BasicSingleEraDateTimeField("AM");
/** The lowest year that can be fully supported. */
private static final int MIN_YEAR = -292269337;
/** The highest year that can be fully supported. */
private static final int MAX_YEAR = 292272708;
/** Cache of zone to chronology arrays */
private static final Map cCache = new HashMap();
/** Singleton instance of a UTC CopticChronology */
private static final CopticChronology INSTANCE_UTC;
static {
// init after static fields
INSTANCE_UTC = getInstance(DateTimeZone.UTC);
}
//-----------------------------------------------------------------------
/**
* Gets an instance of the CopticChronology.
* The time zone of the returned instance is UTC.
*
* @return a singleton UTC instance of the chronology
*/
public static CopticChronology getInstanceUTC() {
return INSTANCE_UTC;
}
/**
* Gets an instance of the CopticChronology in the default time zone.
*
* @return a chronology in the default time zone
*/
public static CopticChronology getInstance() {
return getInstance(DateTimeZone.getDefault(), 4);
}
/**
* Gets an instance of the CopticChronology in the given time zone.
*
* @param zone the time zone to get the chronology in, null is default
* @return a chronology in the specified time zone
*/
public static CopticChronology getInstance(DateTimeZone zone) {
return getInstance(zone, 4);
}
/**
* Gets an instance of the CopticChronology in the given time zone.
*
* @param zone the time zone to get the chronology in, null is default
* @param minDaysInFirstWeek minimum number of days in first week of the year; default is 4
* @return a chronology in the specified time zone
*/
public static CopticChronology getInstance(DateTimeZone zone, int minDaysInFirstWeek) {
if (zone == null) {
zone = DateTimeZone.getDefault();
}
CopticChronology chrono;
synchronized (cCache) {
CopticChronology[] chronos = cCache.get(zone);
if (chronos == null) {
chronos = new CopticChronology[7];
cCache.put(zone, chronos);
}
try {
chrono = chronos[minDaysInFirstWeek - 1];
} catch (ArrayIndexOutOfBoundsException e) {
throw new IllegalArgumentException
("Invalid min days in first week: " + minDaysInFirstWeek);
}
if (chrono == null) {
if (zone == DateTimeZone.UTC) {
// First create without a lower limit.
chrono = new CopticChronology(null, null, minDaysInFirstWeek);
// Impose lower limit and make another CopticChronology.
DateTime lowerLimit = new DateTime(1, 1, 1, 0, 0, 0, 0, chrono);
chrono = new CopticChronology
(LimitChronology.getInstance(chrono, lowerLimit, null),
null, minDaysInFirstWeek);
} else {
chrono = getInstance(DateTimeZone.UTC, minDaysInFirstWeek);
chrono = new CopticChronology
(ZonedChronology.getInstance(chrono, zone), null, minDaysInFirstWeek);
}
chronos[minDaysInFirstWeek - 1] = chrono;
}
}
return chrono;
}
// Constructors and instance variables
//-----------------------------------------------------------------------
/**
* Restricted constructor.
*/
CopticChronology(Chronology base, Object param, int minDaysInFirstWeek) {
super(base, param, minDaysInFirstWeek);
}
/**
* Serialization singleton.
*/
private Object readResolve() {
Chronology base = getBase();
int minDays = getMinimumDaysInFirstWeek();
minDays = (minDays == 0 ? 4 : minDays); // handle rename of BaseGJChronology
return base == null ?
getInstance(DateTimeZone.UTC, minDays) :
getInstance(base.getZone(), minDays);
}
// Conversion
//-----------------------------------------------------------------------
/**
* Gets the Chronology in the UTC time zone.
*
* @return the chronology in UTC
*/
public Chronology withUTC() {
return INSTANCE_UTC;
}
/**
* Gets the Chronology in a specific time zone.
*
* @param zone the zone to get the chronology in, null is default
* @return the chronology
*/
public Chronology withZone(DateTimeZone zone) {
if (zone == null) {
zone = DateTimeZone.getDefault();
}
if (zone == getZone()) {
return this;
}
return getInstance(zone);
}
//-----------------------------------------------------------------------
long calculateFirstDayOfYearMillis(int year) {
// Java epoch is 1970-01-01 Gregorian which is 1686-04-23 Coptic.
// Calculate relative to the nearest leap year and account for the
// difference later.
int relativeYear = year - 1687;
int leapYears;
if (relativeYear <= 0) {
// Add 3 before shifting right since /4 and >>2 behave differently
// on negative numbers.
leapYears = (relativeYear + 3) >> 2;
} else {
leapYears = relativeYear >> 2;
// For post 1687 an adjustment is needed as jan1st is before leap day
if (!isLeapYear(year)) {
leapYears++;
}
}
long millis = (relativeYear * 365L + leapYears)
* (long)DateTimeConstants.MILLIS_PER_DAY;
// Adjust to account for difference between 1687-01-01 and 1686-04-23.
return millis + (365L - 112) * DateTimeConstants.MILLIS_PER_DAY;
}
//-----------------------------------------------------------------------
int getMinYear() {
return MIN_YEAR;
}
//-----------------------------------------------------------------------
int getMaxYear() {
return MAX_YEAR;
}
//-----------------------------------------------------------------------
long getApproxMillisAtEpochDividedByTwo() {
return (1686L * MILLIS_PER_YEAR + 112L * DateTimeConstants.MILLIS_PER_DAY) / 2;
}
//-----------------------------------------------------------------------
protected void assemble(Fields fields) {
if (getBase() == null) {
super.assemble(fields);
// Coptic, like Julian, has no year zero.
fields.year = new SkipDateTimeField(this, fields.year);
fields.weekyear = new SkipDateTimeField(this, fields.weekyear);
fields.era = ERA_FIELD;
fields.monthOfYear = new BasicMonthOfYearDateTimeField(this, 13);
fields.months = fields.monthOfYear.getDurationField();
}
}
}