/*
* Copyright 2001-2005 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.goda.time.chrono;
import java.util.HashMap;
import java.util.Map;
import org.goda.time.Chronology;
import org.goda.time.DateTimeConstants;
import org.goda.time.DateTimeFieldType;
import org.goda.time.DateTimeZone;
import org.goda.time.IllegalFieldValueException;
import org.goda.time.field.SkipDateTimeField;
/**
* Implements a pure proleptic Julian calendar system, which defines every
* fourth year as leap. This implementation follows the leap year rule
* strictly, even for dates before 8 CE, where leap years were actually
* irregular. In the Julian calendar, year zero does not exist: 1 BCE is
* followed by 1 CE.
* <p>
* Although the Julian calendar did not exist before 45 BCE, this chronology
* assumes it did, thus it is proleptic. This implementation also fixes the
* start of the year at January 1.
* <p>
* JulianChronology is thread-safe and immutable.
*
* @see <a href="http://en.wikipedia.org/wiki/Julian_calendar">Wikipedia</a>
* @see GregorianChronology
* @see GJChronology
*
* @author Guy Allard
* @author Brian S O'Neill
* @author Stephen Colebourne
* @since 1.0
*/
public final class JulianChronology extends BasicGJChronology {
/** Serialization lock */
private static final long serialVersionUID = -8731039522547897247L;
private static final long MILLIS_PER_YEAR =
(long) (365.25 * DateTimeConstants.MILLIS_PER_DAY);
private static final long MILLIS_PER_MONTH =
(long) (365.25 * DateTimeConstants.MILLIS_PER_DAY / 12);
/** The lowest year that can be fully supported. */
private static final int MIN_YEAR = -292269054;
/** The highest year that can be fully supported. */
private static final int MAX_YEAR = 292272992;
/** Singleton instance of a UTC JulianChronology */
private static final JulianChronology INSTANCE_UTC;
/** Cache of zone to chronology arrays */
private static final Map<DateTimeZone, Chronology[]> cCache = new HashMap<DateTimeZone, Chronology[]>();
static {
INSTANCE_UTC = getInstance(DateTimeZone.UTC);
}
static int adjustYearForSet(int year) {
if (year <= 0) {
if (year == 0) {
throw new IllegalFieldValueException
(DateTimeFieldType.year(), new Integer(year), null, null);
}
year++;
}
return year;
}
/**
* Gets an instance of the JulianChronology.
* The time zone of the returned instance is UTC.
*
* @return a singleton UTC instance of the chronology
*/
public static JulianChronology getInstanceUTC() {
return INSTANCE_UTC;
}
/**
* Gets an instance of the JulianChronology in the default time zone.
*
* @return a chronology in the default time zone
*/
public static JulianChronology getInstance() {
return getInstance(DateTimeZone.getDefault(), 4);
}
/**
* Gets an instance of the JulianChronology 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 JulianChronology getInstance(DateTimeZone zone) {
return getInstance(zone, 4);
}
/**
* Gets an instance of the JulianChronology 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 JulianChronology getInstance(DateTimeZone zone, int minDaysInFirstWeek) {
if (zone == null) {
zone = DateTimeZone.getDefault();
}
JulianChronology chrono;
synchronized (cCache) {
JulianChronology[] chronos = (JulianChronology[]) cCache.get(zone);
if (chronos == null) {
chronos = new JulianChronology[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) {
chrono = new JulianChronology(null, null, minDaysInFirstWeek);
} else {
chrono = getInstance(DateTimeZone.UTC, minDaysInFirstWeek);
chrono = new JulianChronology
(ZonedChronology.getInstance(chrono, zone), null, minDaysInFirstWeek);
}
chronos[minDaysInFirstWeek - 1] = chrono;
}
}
return chrono;
}
// Constructors and instance variables
//-----------------------------------------------------------------------
/**
* Restricted constructor
*/
JulianChronology(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 getDateMidnightMillis(int year, int monthOfYear, int dayOfMonth)
throws IllegalArgumentException
{
return super.getDateMidnightMillis(adjustYearForSet(year), monthOfYear, dayOfMonth);
}
boolean isLeapYear(int year) {
return (year & 3) == 0;
}
long calculateFirstDayOfYearMillis(int year) {
// Java epoch is 1970-01-01 Gregorian which is 1969-12-19 Julian.
// Calculate relative to the nearest leap year and account for the
// difference later.
int relativeYear = year - 1968;
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 1968 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 1968-01-01 and 1969-12-19.
return millis - (366L + 352) * DateTimeConstants.MILLIS_PER_DAY;
}
int getMinYear() {
return MIN_YEAR;
}
int getMaxYear() {
return MAX_YEAR;
}
long getAverageMillisPerYear() {
return MILLIS_PER_YEAR;
}
long getAverageMillisPerYearDividedByTwo() {
return MILLIS_PER_YEAR / 2;
}
long getAverageMillisPerMonth() {
return MILLIS_PER_MONTH;
}
long getApproxMillisAtEpochDividedByTwo() {
return (1969L * MILLIS_PER_YEAR + 352L * DateTimeConstants.MILLIS_PER_DAY) / 2;
}
protected void assemble(Fields fields) {
if (getBase() == null) {
super.assemble(fields);
// Julian chronology has no year zero.
fields.year = new SkipDateTimeField(this, fields.year);
fields.weekyear = new SkipDateTimeField(this, fields.weekyear);
}
}
}