| 1 | /* |
| 2 | * Copyright 2001-2005 Stephen Colebourne |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.joda.time.chrono; |
| 17 | |
| 18 | import java.util.HashMap; |
| 19 | import java.util.Map; |
| 20 | |
| 21 | import org.joda.time.Chronology; |
| 22 | import org.joda.time.DateTimeConstants; |
| 23 | import org.joda.time.DateTimeFieldType; |
| 24 | import org.joda.time.DateTimeZone; |
| 25 | import org.joda.time.IllegalFieldValueException; |
| 26 | import org.joda.time.field.SkipDateTimeField; |
| 27 | |
| 28 | /** |
| 29 | * Implements a pure proleptic Julian calendar system, which defines every |
| 30 | * fourth year as leap. This implementation follows the leap year rule |
| 31 | * strictly, even for dates before 8 CE, where leap years were actually |
| 32 | * irregular. In the Julian calendar, year zero does not exist: 1 BCE is |
| 33 | * followed by 1 CE. |
| 34 | * <p> |
| 35 | * Although the Julian calendar did not exist before 45 BCE, this chronology |
| 36 | * assumes it did, thus it is proleptic. This implementation also fixes the |
| 37 | * start of the year at January 1. |
| 38 | * <p> |
| 39 | * JulianChronology is thread-safe and immutable. |
| 40 | * |
| 41 | * @see <a href="http://en.wikipedia.org/wiki/Julian_calendar">Wikipedia</a> |
| 42 | * @see GregorianChronology |
| 43 | * @see GJChronology |
| 44 | * |
| 45 | * @author Guy Allard |
| 46 | * @author Brian S O'Neill |
| 47 | * @author Stephen Colebourne |
| 48 | * @since 1.0 |
| 49 | */ |
| 50 | public final class JulianChronology extends BasicGJChronology { |
| 51 | |
| 52 | /** Serialization lock */ |
| 53 | private static final long serialVersionUID = -8731039522547897247L; |
| 54 | |
| 55 | private static final long MILLIS_PER_YEAR = |
| 56 | (long) (365.25 * DateTimeConstants.MILLIS_PER_DAY); |
| 57 | |
| 58 | private static final long MILLIS_PER_MONTH = |
| 59 | (long) (365.25 * DateTimeConstants.MILLIS_PER_DAY / 12); |
| 60 | |
| 61 | /** The lowest year that can be fully supported. */ |
| 62 | private static final int MIN_YEAR = -292269054; |
| 63 | |
| 64 | /** The highest year that can be fully supported. */ |
| 65 | private static final int MAX_YEAR = 292272992; |
| 66 | |
| 67 | /** Singleton instance of a UTC JulianChronology */ |
| 68 | private static final JulianChronology INSTANCE_UTC; |
| 69 | |
| 70 | /** Cache of zone to chronology arrays */ |
| 71 | private static final Map cCache = new HashMap(); |
| 72 | |
| 73 | static { |
| 74 | INSTANCE_UTC = getInstance(DateTimeZone.UTC); |
| 75 | } |
| 76 | |
| 77 | static int adjustYearForSet(int year) { |
| 78 | if (year <= 0) { |
| 79 | if (year == 0) { |
| 80 | throw new IllegalFieldValueException |
| 81 | (DateTimeFieldType.year(), new Integer(year), null, null); |
| 82 | } |
| 83 | year++; |
| 84 | } |
| 85 | return year; |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Gets an instance of the JulianChronology. |
| 90 | * The time zone of the returned instance is UTC. |
| 91 | * |
| 92 | * @return a singleton UTC instance of the chronology |
| 93 | */ |
| 94 | public static JulianChronology getInstanceUTC() { |
| 95 | return INSTANCE_UTC; |
| 96 | } |
| 97 | |
| 98 | /** |
| 99 | * Gets an instance of the JulianChronology in the default time zone. |
| 100 | * |
| 101 | * @return a chronology in the default time zone |
| 102 | */ |
| 103 | public static JulianChronology getInstance() { |
| 104 | return getInstance(DateTimeZone.getDefault(), 4); |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * Gets an instance of the JulianChronology in the given time zone. |
| 109 | * |
| 110 | * @param zone the time zone to get the chronology in, null is default |
| 111 | * @return a chronology in the specified time zone |
| 112 | */ |
| 113 | public static JulianChronology getInstance(DateTimeZone zone) { |
| 114 | return getInstance(zone, 4); |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * Gets an instance of the JulianChronology in the given time zone. |
| 119 | * |
| 120 | * @param zone the time zone to get the chronology in, null is default |
| 121 | * @param minDaysInFirstWeek minimum number of days in first week of the year; default is 4 |
| 122 | * @return a chronology in the specified time zone |
| 123 | */ |
| 124 | public static JulianChronology getInstance(DateTimeZone zone, int minDaysInFirstWeek) { |
| 125 | if (zone == null) { |
| 126 | zone = DateTimeZone.getDefault(); |
| 127 | } |
| 128 | JulianChronology chrono; |
| 129 | synchronized (cCache) { |
| 130 | JulianChronology[] chronos = (JulianChronology[]) cCache.get(zone); |
| 131 | if (chronos == null) { |
| 132 | chronos = new JulianChronology[7]; |
| 133 | cCache.put(zone, chronos); |
| 134 | } |
| 135 | try { |
| 136 | chrono = chronos[minDaysInFirstWeek - 1]; |
| 137 | } catch (ArrayIndexOutOfBoundsException e) { |
| 138 | throw new IllegalArgumentException |
| 139 | ("Invalid min days in first week: " + minDaysInFirstWeek); |
| 140 | } |
| 141 | if (chrono == null) { |
| 142 | if (zone == DateTimeZone.UTC) { |
| 143 | chrono = new JulianChronology(null, null, minDaysInFirstWeek); |
| 144 | } else { |
| 145 | chrono = getInstance(DateTimeZone.UTC, minDaysInFirstWeek); |
| 146 | chrono = new JulianChronology |
| 147 | (ZonedChronology.getInstance(chrono, zone), null, minDaysInFirstWeek); |
| 148 | } |
| 149 | chronos[minDaysInFirstWeek - 1] = chrono; |
| 150 | } |
| 151 | } |
| 152 | return chrono; |
| 153 | } |
| 154 | |
| 155 | // Constructors and instance variables |
| 156 | //----------------------------------------------------------------------- |
| 157 | |
| 158 | /** |
| 159 | * Restricted constructor |
| 160 | */ |
| 161 | JulianChronology(Chronology base, Object param, int minDaysInFirstWeek) { |
| 162 | super(base, param, minDaysInFirstWeek); |
| 163 | } |
| 164 | |
| 165 | /** |
| 166 | * Serialization singleton |
| 167 | */ |
| 168 | private Object readResolve() { |
| 169 | Chronology base = getBase(); |
| 170 | int minDays = getMinimumDaysInFirstWeek(); |
| 171 | minDays = (minDays == 0 ? 4 : minDays); // handle rename of BaseGJChronology |
| 172 | return base == null ? |
| 173 | getInstance(DateTimeZone.UTC, minDays) : |
| 174 | getInstance(base.getZone(), minDays); |
| 175 | } |
| 176 | |
| 177 | // Conversion |
| 178 | //----------------------------------------------------------------------- |
| 179 | /** |
| 180 | * Gets the Chronology in the UTC time zone. |
| 181 | * |
| 182 | * @return the chronology in UTC |
| 183 | */ |
| 184 | public Chronology withUTC() { |
| 185 | return INSTANCE_UTC; |
| 186 | } |
| 187 | |
| 188 | /** |
| 189 | * Gets the Chronology in a specific time zone. |
| 190 | * |
| 191 | * @param zone the zone to get the chronology in, null is default |
| 192 | * @return the chronology |
| 193 | */ |
| 194 | public Chronology withZone(DateTimeZone zone) { |
| 195 | if (zone == null) { |
| 196 | zone = DateTimeZone.getDefault(); |
| 197 | } |
| 198 | if (zone == getZone()) { |
| 199 | return this; |
| 200 | } |
| 201 | return getInstance(zone); |
| 202 | } |
| 203 | |
| 204 | long getDateMidnightMillis(int year, int monthOfYear, int dayOfMonth) |
| 205 | throws IllegalArgumentException |
| 206 | { |
| 207 | return super.getDateMidnightMillis(adjustYearForSet(year), monthOfYear, dayOfMonth); |
| 208 | } |
| 209 | |
| 210 | boolean isLeapYear(int year) { |
| 211 | return (year & 3) == 0; |
| 212 | } |
| 213 | |
| 214 | long calculateFirstDayOfYearMillis(int year) { |
| 215 | // Java epoch is 1970-01-01 Gregorian which is 1969-12-19 Julian. |
| 216 | // Calculate relative to the nearest leap year and account for the |
| 217 | // difference later. |
| 218 | |
| 219 | int relativeYear = year - 1968; |
| 220 | int leapYears; |
| 221 | if (relativeYear <= 0) { |
| 222 | // Add 3 before shifting right since /4 and >>2 behave differently |
| 223 | // on negative numbers. |
| 224 | leapYears = (relativeYear + 3) >> 2; |
| 225 | } else { |
| 226 | leapYears = relativeYear >> 2; |
| 227 | // For post 1968 an adjustment is needed as jan1st is before leap day |
| 228 | if (!isLeapYear(year)) { |
| 229 | leapYears++; |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | long millis = (relativeYear * 365L + leapYears) * (long)DateTimeConstants.MILLIS_PER_DAY; |
| 234 | |
| 235 | // Adjust to account for difference between 1968-01-01 and 1969-12-19. |
| 236 | |
| 237 | return millis - (366L + 352) * DateTimeConstants.MILLIS_PER_DAY; |
| 238 | } |
| 239 | |
| 240 | int getMinYear() { |
| 241 | return MIN_YEAR; |
| 242 | } |
| 243 | |
| 244 | int getMaxYear() { |
| 245 | return MAX_YEAR; |
| 246 | } |
| 247 | |
| 248 | long getAverageMillisPerYear() { |
| 249 | return MILLIS_PER_YEAR; |
| 250 | } |
| 251 | |
| 252 | long getAverageMillisPerYearDividedByTwo() { |
| 253 | return MILLIS_PER_YEAR / 2; |
| 254 | } |
| 255 | |
| 256 | long getAverageMillisPerMonth() { |
| 257 | return MILLIS_PER_MONTH; |
| 258 | } |
| 259 | |
| 260 | long getApproxMillisAtEpochDividedByTwo() { |
| 261 | return (1969L * MILLIS_PER_YEAR + 352L * DateTimeConstants.MILLIS_PER_DAY) / 2; |
| 262 | } |
| 263 | |
| 264 | protected void assemble(Fields fields) { |
| 265 | if (getBase() == null) { |
| 266 | super.assemble(fields); |
| 267 | // Julian chronology has no year zero. |
| 268 | fields.year = new SkipDateTimeField(this, fields.year); |
| 269 | fields.weekyear = new SkipDateTimeField(this, fields.weekyear); |
| 270 | } |
| 271 | } |
| 272 | |
| 273 | } |