| 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.DateTimeZone; |
| 24 | |
| 25 | /** |
| 26 | * Implements a pure proleptic Gregorian calendar system, which defines every |
| 27 | * fourth year as leap, unless the year is divisible by 100 and not by 400. |
| 28 | * This improves upon the Julian calendar leap year rule. |
| 29 | * <p> |
| 30 | * Although the Gregorian calendar did not exist before 1582 CE, this |
| 31 | * chronology assumes it did, thus it is proleptic. This implementation also |
| 32 | * fixes the start of the year at January 1, and defines the year zero. |
| 33 | * <p> |
| 34 | * GregorianChronology is thread-safe and immutable. |
| 35 | * |
| 36 | * @see <a href="http://en.wikipedia.org/wiki/Gregorian_calendar">Wikipedia</a> |
| 37 | * @see JulianChronology |
| 38 | * @see GJChronology |
| 39 | * |
| 40 | * @author Guy Allard |
| 41 | * @author Stephen Colebourne |
| 42 | * @author Brian S O'Neill |
| 43 | * @since 1.0 |
| 44 | */ |
| 45 | public final class GregorianChronology extends BasicGJChronology { |
| 46 | |
| 47 | /** Serialization lock */ |
| 48 | private static final long serialVersionUID = -861407383323710522L; |
| 49 | |
| 50 | private static final long MILLIS_PER_YEAR = |
| 51 | (long) (365.2425 * DateTimeConstants.MILLIS_PER_DAY); |
| 52 | |
| 53 | private static final long MILLIS_PER_MONTH = |
| 54 | (long) (365.2425 * DateTimeConstants.MILLIS_PER_DAY / 12); |
| 55 | |
| 56 | private static final int DAYS_0000_TO_1970 = 719527; |
| 57 | |
| 58 | /** The lowest year that can be fully supported. */ |
| 59 | private static final int MIN_YEAR = -292275054; |
| 60 | |
| 61 | /** The highest year that can be fully supported. */ |
| 62 | private static final int MAX_YEAR = 292278993; |
| 63 | |
| 64 | /** Singleton instance of a UTC GregorianChronology */ |
| 65 | private static final GregorianChronology INSTANCE_UTC; |
| 66 | |
| 67 | /** Cache of zone to chronology arrays */ |
| 68 | private static final Map cCache = new HashMap(); |
| 69 | |
| 70 | static { |
| 71 | INSTANCE_UTC = getInstance(DateTimeZone.UTC); |
| 72 | } |
| 73 | |
| 74 | /** |
| 75 | * Gets an instance of the GregorianChronology. |
| 76 | * The time zone of the returned instance is UTC. |
| 77 | * |
| 78 | * @return a singleton UTC instance of the chronology |
| 79 | */ |
| 80 | public static GregorianChronology getInstanceUTC() { |
| 81 | return INSTANCE_UTC; |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Gets an instance of the GregorianChronology in the default time zone. |
| 86 | * |
| 87 | * @return a chronology in the default time zone |
| 88 | */ |
| 89 | public static GregorianChronology getInstance() { |
| 90 | return getInstance(DateTimeZone.getDefault(), 4); |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * Gets an instance of the GregorianChronology in the given time zone. |
| 95 | * |
| 96 | * @param zone the time zone to get the chronology in, null is default |
| 97 | * @return a chronology in the specified time zone |
| 98 | */ |
| 99 | public static GregorianChronology getInstance(DateTimeZone zone) { |
| 100 | return getInstance(zone, 4); |
| 101 | } |
| 102 | |
| 103 | /** |
| 104 | * Gets an instance of the GregorianChronology in the given time zone. |
| 105 | * |
| 106 | * @param zone the time zone to get the chronology in, null is default |
| 107 | * @param minDaysInFirstWeek minimum number of days in first week of the year; default is 4 |
| 108 | * @return a chronology in the specified time zone |
| 109 | */ |
| 110 | public static GregorianChronology getInstance(DateTimeZone zone, int minDaysInFirstWeek) { |
| 111 | if (zone == null) { |
| 112 | zone = DateTimeZone.getDefault(); |
| 113 | } |
| 114 | GregorianChronology chrono; |
| 115 | synchronized (cCache) { |
| 116 | GregorianChronology[] chronos = (GregorianChronology[]) cCache.get(zone); |
| 117 | if (chronos == null) { |
| 118 | chronos = new GregorianChronology[7]; |
| 119 | cCache.put(zone, chronos); |
| 120 | } |
| 121 | try { |
| 122 | chrono = chronos[minDaysInFirstWeek - 1]; |
| 123 | } catch (ArrayIndexOutOfBoundsException e) { |
| 124 | throw new IllegalArgumentException |
| 125 | ("Invalid min days in first week: " + minDaysInFirstWeek); |
| 126 | } |
| 127 | if (chrono == null) { |
| 128 | if (zone == DateTimeZone.UTC) { |
| 129 | chrono = new GregorianChronology(null, null, minDaysInFirstWeek); |
| 130 | } else { |
| 131 | chrono = getInstance(DateTimeZone.UTC, minDaysInFirstWeek); |
| 132 | chrono = new GregorianChronology |
| 133 | (ZonedChronology.getInstance(chrono, zone), null, minDaysInFirstWeek); |
| 134 | } |
| 135 | chronos[minDaysInFirstWeek - 1] = chrono; |
| 136 | } |
| 137 | } |
| 138 | return chrono; |
| 139 | } |
| 140 | |
| 141 | // Constructors and instance variables |
| 142 | //----------------------------------------------------------------------- |
| 143 | |
| 144 | /** |
| 145 | * Restricted constructor |
| 146 | */ |
| 147 | private GregorianChronology(Chronology base, Object param, int minDaysInFirstWeek) { |
| 148 | super(base, param, minDaysInFirstWeek); |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * Serialization singleton |
| 153 | */ |
| 154 | private Object readResolve() { |
| 155 | Chronology base = getBase(); |
| 156 | int minDays = getMinimumDaysInFirstWeek(); |
| 157 | minDays = (minDays == 0 ? 4 : minDays); // handle rename of BaseGJChronology |
| 158 | return base == null ? |
| 159 | getInstance(DateTimeZone.UTC, minDays) : |
| 160 | getInstance(base.getZone(), minDays); |
| 161 | } |
| 162 | |
| 163 | // Conversion |
| 164 | //----------------------------------------------------------------------- |
| 165 | /** |
| 166 | * Gets the Chronology in the UTC time zone. |
| 167 | * |
| 168 | * @return the chronology in UTC |
| 169 | */ |
| 170 | public Chronology withUTC() { |
| 171 | return INSTANCE_UTC; |
| 172 | } |
| 173 | |
| 174 | /** |
| 175 | * Gets the Chronology in a specific time zone. |
| 176 | * |
| 177 | * @param zone the zone to get the chronology in, null is default |
| 178 | * @return the chronology |
| 179 | */ |
| 180 | public Chronology withZone(DateTimeZone zone) { |
| 181 | if (zone == null) { |
| 182 | zone = DateTimeZone.getDefault(); |
| 183 | } |
| 184 | if (zone == getZone()) { |
| 185 | return this; |
| 186 | } |
| 187 | return getInstance(zone); |
| 188 | } |
| 189 | |
| 190 | protected void assemble(Fields fields) { |
| 191 | if (getBase() == null) { |
| 192 | super.assemble(fields); |
| 193 | } |
| 194 | } |
| 195 | |
| 196 | boolean isLeapYear(int year) { |
| 197 | return ((year & 3) == 0) && ((year % 100) != 0 || (year % 400) == 0); |
| 198 | } |
| 199 | |
| 200 | long calculateFirstDayOfYearMillis(int year) { |
| 201 | // Initial value is just temporary. |
| 202 | int leapYears = year / 100; |
| 203 | if (year < 0) { |
| 204 | // Add 3 before shifting right since /4 and >>2 behave differently |
| 205 | // on negative numbers. When the expression is written as |
| 206 | // (year / 4) - (year / 100) + (year / 400), |
| 207 | // it works for both positive and negative values, except this optimization |
| 208 | // eliminates two divisions. |
| 209 | leapYears = ((year + 3) >> 2) - leapYears + ((leapYears + 3) >> 2) - 1; |
| 210 | } else { |
| 211 | leapYears = (year >> 2) - leapYears + (leapYears >> 2); |
| 212 | if (isLeapYear(year)) { |
| 213 | leapYears--; |
| 214 | } |
| 215 | } |
| 216 | |
| 217 | return (year * 365L + (leapYears - DAYS_0000_TO_1970)) * DateTimeConstants.MILLIS_PER_DAY; |
| 218 | } |
| 219 | |
| 220 | int getMinYear() { |
| 221 | return MIN_YEAR; |
| 222 | } |
| 223 | |
| 224 | int getMaxYear() { |
| 225 | return MAX_YEAR; |
| 226 | } |
| 227 | |
| 228 | long getAverageMillisPerYear() { |
| 229 | return MILLIS_PER_YEAR; |
| 230 | } |
| 231 | |
| 232 | long getAverageMillisPerYearDividedByTwo() { |
| 233 | return MILLIS_PER_YEAR / 2; |
| 234 | } |
| 235 | |
| 236 | long getAverageMillisPerMonth() { |
| 237 | return MILLIS_PER_MONTH; |
| 238 | } |
| 239 | |
| 240 | long getApproxMillisAtEpochDividedByTwo() { |
| 241 | return (1970L * MILLIS_PER_YEAR) / 2; |
| 242 | } |
| 243 | |
| 244 | } |