Java tutorial
/* * Copyright 2001-2014 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.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.concurrent.ConcurrentHashMap; import org.joda.time.Chronology; import org.joda.time.DateTimeFieldType; import org.joda.time.DateTimeZone; import org.joda.time.field.DividedDateTimeField; import org.joda.time.field.RemainderDateTimeField; /** * Implements a chronology that follows the rules of the ISO8601 standard, * which is compatible with Gregorian for all modern dates. * When ISO does not define a field, but it can be determined (such as AM/PM) * it is included. * <p> * With the exception of century related fields, ISOChronology is exactly the * same as {@link GregorianChronology}. In this chronology, centuries and year * of century are zero based. For all years, the century is determined by * dropping the last two digits of the year, ignoring sign. The year of century * is the value of the last two year digits. * <p> * ISOChronology is thread-safe and immutable. * * @author Stephen Colebourne * @author Brian S O'Neill * @since 1.0 */ public final class ISOChronology extends AssembledChronology { /** Serialization lock */ private static final long serialVersionUID = -6212696554273812441L; /** Singleton instance of a UTC ISOChronology */ private static final ISOChronology INSTANCE_UTC; /** Cache of zone to chronology */ private static final ConcurrentHashMap<DateTimeZone, ISOChronology> cCache = new ConcurrentHashMap<DateTimeZone, ISOChronology>(); static { INSTANCE_UTC = new ISOChronology(GregorianChronology.getInstanceUTC()); cCache.put(DateTimeZone.UTC, INSTANCE_UTC); } /** * Gets an instance of the ISOChronology. * The time zone of the returned instance is UTC. * * @return a singleton UTC instance of the chronology */ public static ISOChronology getInstanceUTC() { return INSTANCE_UTC; } /** * Gets an instance of the ISOChronology in the default time zone. * * @return a chronology in the default time zone */ public static ISOChronology getInstance() { return getInstance(DateTimeZone.getDefault()); } /** * Gets an instance of the ISOChronology 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 ISOChronology getInstance(DateTimeZone zone) { if (zone == null) { zone = DateTimeZone.getDefault(); } ISOChronology chrono = cCache.get(zone); if (chrono == null) { chrono = new ISOChronology(ZonedChronology.getInstance(INSTANCE_UTC, zone)); ISOChronology oldChrono = cCache.putIfAbsent(zone, chrono); if (oldChrono != null) { chrono = oldChrono; } } return chrono; } // Constructors and instance variables //----------------------------------------------------------------------- /** * Restricted constructor */ private ISOChronology(Chronology base) { super(base, null); } // 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); } // Output //----------------------------------------------------------------------- /** * Gets a debugging toString. * * @return a debugging string */ public String toString() { String str = "ISOChronology"; DateTimeZone zone = getZone(); if (zone != null) { str = str + '[' + zone.getID() + ']'; } return str; } protected void assemble(Fields fields) { if (getBase().getZone() == DateTimeZone.UTC) { // Use zero based century and year of century. fields.centuryOfEra = new DividedDateTimeField(ISOYearOfEraDateTimeField.INSTANCE, DateTimeFieldType.centuryOfEra(), 100); fields.centuries = fields.centuryOfEra.getDurationField(); fields.yearOfCentury = new RemainderDateTimeField((DividedDateTimeField) fields.centuryOfEra, DateTimeFieldType.yearOfCentury()); fields.weekyearOfCentury = new RemainderDateTimeField((DividedDateTimeField) fields.centuryOfEra, fields.weekyears, DateTimeFieldType.weekyearOfCentury()); } } //----------------------------------------------------------------------- /** * Checks if this chronology instance equals another. * * @param obj the object to compare to * @return true if equal * @since 1.6 */ public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof ISOChronology) { ISOChronology chrono = (ISOChronology) obj; return getZone().equals(chrono.getZone()); } return false; } /** * A suitable hash code for the chronology. * * @return the hash code * @since 1.6 */ public int hashCode() { return "ISO".hashCode() * 11 + getZone().hashCode(); } //----------------------------------------------------------------------- /** * Serialize ISOChronology instances using a small stub. This reduces the * serialized size, and deserialized instances come from the cache. */ private Object writeReplace() { return new Stub(getZone()); } private static final class Stub implements Serializable { private static final long serialVersionUID = -6212696554273812441L; private transient DateTimeZone iZone; Stub(DateTimeZone zone) { iZone = zone; } private Object readResolve() { return ISOChronology.getInstance(iZone); } private void writeObject(ObjectOutputStream out) throws IOException { out.writeObject(iZone); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { iZone = (DateTimeZone) in.readObject(); } } }