ChronoLocalDate.java
/*
* Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of JSR-310 nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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package org.threeten.bp.chrono;
import static org.threeten.bp.temporal.ChronoField.DAY_OF_MONTH;
import static org.threeten.bp.temporal.ChronoField.EPOCH_DAY;
import static org.threeten.bp.temporal.ChronoField.ERA;
import static org.threeten.bp.temporal.ChronoField.MONTH_OF_YEAR;
import static org.threeten.bp.temporal.ChronoField.YEAR;
import static org.threeten.bp.temporal.ChronoField.YEAR_OF_ERA;
import java.util.Comparator;
import org.threeten.bp.DateTimeException;
import org.threeten.bp.LocalDate;
import org.threeten.bp.LocalTime;
import org.threeten.bp.format.DateTimeFormatter;
import org.threeten.bp.jdk8.DefaultInterfaceTemporal;
import org.threeten.bp.jdk8.Jdk8Methods;
import org.threeten.bp.temporal.ChronoField;
import org.threeten.bp.temporal.ChronoUnit;
import org.threeten.bp.temporal.Temporal;
import org.threeten.bp.temporal.TemporalAccessor;
import org.threeten.bp.temporal.TemporalAdjuster;
import org.threeten.bp.temporal.TemporalAmount;
import org.threeten.bp.temporal.TemporalField;
import org.threeten.bp.temporal.TemporalQueries;
import org.threeten.bp.temporal.TemporalQuery;
import org.threeten.bp.temporal.TemporalUnit;
/**
* A date without time-of-day or time-zone in an arbitrary chronology, intended
* for advanced globalization use cases.
* <p>
* <b>Most applications should declare method signatures, fields and variables
* as {@link LocalDate}, not this interface.</b>
* <p>
* A {@code ChronoLocalDate} is the abstract representation of a date where the
* {@code Chronology chronology}, or calendar system, is pluggable.
* The date is defined in terms of fields expressed by {@link TemporalField},
* where most common implementations are defined in {@link ChronoField}.
* The chronology defines how the calendar system operates and the meaning of
* the standard fields.
*
* <h4>When to use this interface</h4>
* The design of the API encourages the use of {@code LocalDate} rather than this
* interface, even in the case where the application needs to deal with multiple
* calendar systems. The rationale for this is explored in the following documentation.
* <p>
* The primary use case where this interface should be used is where the generic
* type parameter {@code <C>} is fully defined as a specific chronology.
* In that case, the assumptions of that chronology are known at development
* time and specified in the code.
* <p>
* When the chronology is defined in the generic type parameter as ? or otherwise
* unknown at development time, the rest of the discussion below applies.
* <p>
* To emphasize the point, declaring a method signature, field or variable as this
* interface type can initially seem like the sensible way to globalize an application,
* however it is usually the wrong approach.
* As such, it should be considered an application-wide architectural decision to choose
* to use this interface as opposed to {@code LocalDate}.
*
* <h4>Architectural issues to consider</h4>
* These are some of the points that must be considered before using this interface
* throughout an application.
* <p>
* 1) Applications using this interface, as opposed to using just {@code LocalDate},
* face a significantly higher probability of bugs. This is because the calendar system
* in use is not known at development time. A key cause of bugs is where the developer
* applies assumptions from their day-to-day knowledge of the ISO calendar system
* to code that is intended to deal with any arbitrary calendar system.
* The section below outlines how those assumptions can cause problems
* The primary mechanism for reducing this increased risk of bugs is a strong code review process.
* This should also be considered a extra cost in maintenance for the lifetime of the code.
* <p>
* 2) This interface does not enforce immutability of implementations.
* While the implementation notes indicate that all implementations must be immutable
* there is nothing in the code or type system to enforce this. Any method declared
* to accept a {@code ChronoLocalDate} could therefore be passed a poorly or
* maliciously written mutable implementation.
* <p>
* 3) Applications using this interface must consider the impact of eras.
* {@code LocalDate} shields users from the concept of eras, by ensuring that {@code getYear()}
* returns the proleptic year. That decision ensures that developers can think of
* {@code LocalDate} instances as consisting of three fields - year, month-of-year and day-of-month.
* By contrast, users of this interface must think of dates as consisting of four fields -
* era, year-of-era, month-of-year and day-of-month. The extra era field is frequently
* forgotten, yet it is of vital importance to dates in an arbitrary calendar system.
* For example, in the Japanese calendar system, the era represents the reign of an Emperor.
* Whenever one reign ends and another starts, the year-of-era is reset to one.
* <p>
* 4) The only agreed international standard for passing a date between two systems
* is the ISO-8601 standard which requires the ISO calendar system. Using this interface
* throughout the application will inevitably lead to the requirement to pass the date
* across a network or component boundary, requiring an application specific protocol or format.
* <p>
* 5) Long term persistence, such as a database, will almost always only accept dates in the
* ISO-8601 calendar system (or the related Julian-Gregorian). Passing around dates in other
* calendar systems increases the complications of interacting with persistence.
* <p>
* 6) Most of the time, passing a {@code ChronoLocalDate} throughout an application
* is unnecessary, as discussed in the last section below.
*
* <h4>False assumptions causing bugs in multi-calendar system code</h4>
* As indicated above, there are many issues to consider when try to use and manipulate a
* date in an arbitrary calendar system. These are some of the key issues.
* <p>
* Code that queries the day-of-month and assumes that the value will never be more than
* 31 is invalid. Some calendar systems have more than 31 days in some months.
* <p>
* Code that adds 12 months to a date and assumes that a year has been added is invalid.
* Some calendar systems have a different number of months, such as 13 in the Coptic or Ethiopic.
* <p>
* Code that adds one month to a date and assumes that the month-of-year value will increase
* by one or wrap to the next year is invalid. Some calendar systems have a variable number
* of months in a year, such as the Hebrew.
* <p>
* Code that adds one month, then adds a second one month and assumes that the day-of-month
* will remain close to its original value is invalid. Some calendar systems have a large difference
* between the length of the longest month and the length of the shortest month.
* For example, the Coptic or Ethiopic have 12 months of 30 days and 1 month of 5 days.
* <p>
* Code that adds seven days and assumes that a week has been added is invalid.
* Some calendar systems have weeks of other than seven days, such as the French Revolutionary.
* <p>
* Code that assumes that because the year of {@code date1} is greater than the year of {@code date2}
* then {@code date1} is after {@code date2} is invalid. This is invalid for all calendar systems
* when referring to the year-of-era, and especially untrue of the Japanese calendar system
* where the year-of-era restarts with the reign of every new Emperor.
* <p>
* Code that treats month-of-year one and day-of-month one as the start of the year is invalid.
* Not all calendar systems start the year when the month value is one.
* <p>
* In general, manipulating a date, and even querying a date, is wide open to bugs when the
* calendar system is unknown at development time. This is why it is essential that code using
* this interface is subjected to additional code reviews. It is also why an architectural
* decision to avoid this interface type is usually the correct one.
*
* <h4>Using LocalDate instead</h4>
* The primary alternative to using this interface throughout your application is as follows.
* <p><ul>
* <li>Declare all method signatures referring to dates in terms of {@code LocalDate}.
* <li>Either store the chronology (calendar system) in the user profile or lookup
* the chronology from the user locale
* <li>Convert the ISO {@code LocalDate} to and from the user's preferred calendar system during
* printing and parsing
* </ul><p>
* This approach treats the problem of globalized calendar systems as a localization issue
* and confines it to the UI layer. This approach is in keeping with other localization
* issues in the java platform.
* <p>
* As discussed above, performing calculations on a date where the rules of the calendar system
* are pluggable requires skill and is not recommended.
* Fortunately, the need to perform calculations on a date in an arbitrary calendar system
* is extremely rare. For example, it is highly unlikely that the business rules of a library
* book rental scheme will allow rentals to be for one month, where meaning of the month
* is dependent on the user's preferred calendar system.
* <p>
* A key use case for calculations on a date in an arbitrary calendar system is producing
* a month-by-month calendar for display and user interaction. Again, this is a UI issue,
* and use of this interface solely within a few methods of the UI layer may be justified.
* <p>
* In any other part of the system, where a date must be manipulated in a calendar system
* other than ISO, the use case will generally specify the calendar system to use.
* For example, an application may need to calculate the next Islamic or Hebrew holiday
* which may require manipulating the date.
* This kind of use case can be handled as follows:
* <p><ul>
* <li>start from the ISO {@code LocalDate} being passed to the method
* <li>convert the date to the alternate calendar system, which for this use case is known
* rather than arbitrary
* <li>perform the calculation
* <li>convert back to {@code LocalDate}
* </ul><p>
* Developers writing low-level frameworks or libraries should also avoid this interface.
* Instead, one of the two general purpose access interfaces should be used.
* Use {@link TemporalAccessor} if read-only access is required, or use {@link Temporal}
* if read-write access is required.
*
* <h3>Specification for implementors</h3>
* This interface must be implemented with care to ensure other classes operate correctly.
* All implementations that can be instantiated must be final, immutable and thread-safe.
* Subclasses should be Serializable wherever possible.
* <p>
* Additional calendar systems may be added to the system.
* See {@link Chronology} for more details.
* <p>
* In JDK 8, this is an interface with default methods.
* Since there are no default methods in JDK 7, an abstract class is used.
*/
public abstract class ChronoLocalDate
extends DefaultInterfaceTemporal
implements Temporal, TemporalAdjuster, Comparable<ChronoLocalDate> {
/**
* Gets a comparator that compares {@code ChronoLocalDate} in
* time-line order ignoring the chronology.
* <p>
* This comparator differs from the comparison in {@link #compareTo} in that it
* only compares the underlying date and not the chronology.
* This allows dates in different calendar systems to be compared based
* on the position of the date on the local time-line.
* The underlying comparison is equivalent to comparing the epoch-day.
*
* @return a comparator that compares in time-line order ignoring the chronology
* @see #isAfter
* @see #isBefore
* @see #isEqual
*/
public static Comparator<ChronoLocalDate> timeLineOrder() {
return DATE_COMPARATOR;
}
private static final Comparator<ChronoLocalDate> DATE_COMPARATOR =
new Comparator<ChronoLocalDate>() {
@Override
public int compare(ChronoLocalDate date1, ChronoLocalDate date2) {
return Jdk8Methods.compareLongs(date1.toEpochDay(), date2.toEpochDay());
}
};
//-----------------------------------------------------------------------
/**
* Obtains an instance of {@code ChronoLocalDate} from a temporal object.
* <p>
* This obtains a local date based on the specified temporal.
* A {@code TemporalAccessor} represents an arbitrary set of date and time information,
* which this factory converts to an instance of {@code ChronoLocalDate}.
* <p>
* The conversion extracts and combines the chronology and the date
* from the temporal object. The behavior is equivalent to using
* {@link Chronology#date(TemporalAccessor)} with the extracted chronology.
* Implementations are permitted to perform optimizations such as accessing
* those fields that are equivalent to the relevant objects.
* <p>
* This method matches the signature of the functional interface {@link TemporalQuery}
* allowing it to be used as a query via method reference, {@code ChronoLocalDate::from}.
*
* @param temporal the temporal object to convert, not null
* @return the date, not null
* @throws DateTimeException if unable to convert to a {@code ChronoLocalDate}
* @see Chronology#date(TemporalAccessor)
*/
public static ChronoLocalDate from(TemporalAccessor temporal) {
Jdk8Methods.requireNonNull(temporal, "temporal");
if (temporal instanceof ChronoLocalDate) {
return (ChronoLocalDate) temporal;
}
Chronology chrono = temporal.query(TemporalQueries.chronology());
if (chrono == null) {
throw new DateTimeException("No Chronology found to create ChronoLocalDate: " + temporal.getClass());
}
return chrono.date(temporal);
}
//-----------------------------------------------------------------------
/**
* Gets the chronology of this date.
* <p>
* The {@code Chronology} represents the calendar system in use.
* The era and other fields in {@link ChronoField} are defined by the chronology.
*
* @return the chronology, not null
*/
public abstract Chronology getChronology();
/**
* Gets the era, as defined by the chronology.
* <p>
* The era is, conceptually, the largest division of the time-line.
* Most calendar systems have a single epoch dividing the time-line into two eras.
* However, some have multiple eras, such as one for the reign of each leader.
* The exact meaning is determined by the {@code Chronology}.
* <p>
* All correctly implemented {@code Era} classes are singletons, thus it
* is valid code to write {@code date.getEra() == SomeEra.NAME)}.
*
* @return the chronology specific era constant applicable at this date, not null
*/
public Era getEra() {
return getChronology().eraOf(get(ERA));
}
//-----------------------------------------------------------------------
/**
* Checks if the year is a leap year, as defined by the calendar system.
* <p>
* A leap-year is a year of a longer length than normal.
* The exact meaning is determined by the chronology with the constraint that
* a leap-year must imply a year-length longer than a non leap-year.
* <p>
* The default implementation uses {@link Chronology#isLeapYear(long)}.
*
* @return true if this date is in a leap year, false otherwise
*/
public boolean isLeapYear() {
return getChronology().isLeapYear(getLong(YEAR));
}
/**
* Returns the length of the month represented by this date, as defined by the calendar system.
* <p>
* This returns the length of the month in days.
*
* @return the length of the month in days
*/
public abstract int lengthOfMonth();
/**
* Returns the length of the year represented by this date, as defined by the calendar system.
* <p>
* This returns the length of the year in days.
* <p>
* The default implementation uses {@link #isLeapYear()} and returns 365 or 366.
*
* @return the length of the year in days
*/
public int lengthOfYear() {
return (isLeapYear() ? 366 : 365);
}
@Override
public boolean isSupported(TemporalField field) {
if (field instanceof ChronoField) {
return field.isDateBased();
}
return field != null && field.isSupportedBy(this);
}
@Override
public boolean isSupported(TemporalUnit unit) {
if (unit instanceof ChronoUnit) {
return unit.isDateBased();
}
return unit != null && unit.isSupportedBy(this);
}
//-------------------------------------------------------------------------
// override for covariant return type
@Override
public ChronoLocalDate with(TemporalAdjuster adjuster) {
return getChronology().ensureChronoLocalDate(super.with(adjuster));
}
@Override
public abstract ChronoLocalDate with(TemporalField field, long newValue);
@Override
public ChronoLocalDate plus(TemporalAmount amount) {
return getChronology().ensureChronoLocalDate(super.plus(amount));
}
@Override
public abstract ChronoLocalDate plus(long amountToAdd, TemporalUnit unit);
@Override
public ChronoLocalDate minus(TemporalAmount amount) {
return getChronology().ensureChronoLocalDate(super.minus(amount));
}
@Override
public ChronoLocalDate minus(long amountToSubtract, TemporalUnit unit) {
return getChronology().ensureChronoLocalDate(super.minus(amountToSubtract, unit));
}
//-----------------------------------------------------------------------
@SuppressWarnings("unchecked")
@Override
public <R> R query(TemporalQuery<R> query) {
if (query == TemporalQueries.chronology()) {
return (R) getChronology();
} else if (query == TemporalQueries.precision()) {
return (R) ChronoUnit.DAYS;
} else if (query == TemporalQueries.localDate()) {
return (R) LocalDate.ofEpochDay(toEpochDay());
} else if (query == TemporalQueries.localTime() || query == TemporalQueries.zone() ||
query == TemporalQueries.zoneId() || query == TemporalQueries.offset()) {
return null;
}
return super.query(query);
}
@Override
public Temporal adjustInto(Temporal temporal) {
return temporal.with(EPOCH_DAY, toEpochDay());
}
//-----------------------------------------------------------------------
/**
* Calculates the period between this date and another date as a {@code ChronoPeriod}.
* <p>
* This calculates the period between two dates. All supplied chronologies
* calculate the period using years, months and days, however the
* {@code ChronoPeriod} API allows the period to be represented using other units.
* <p>
* The start and end points are {@code this} and the specified date.
* The result will be negative if the end is before the start.
* The negative sign will be the same in each of year, month and day.
* <p>
* The calculation is performed using the chronology of this date.
* If necessary, the input date will be converted to match.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param endDateExclusive the end date, exclusive, which may be in any chronology, not null
* @return the period between this date and the end date, not null
* @throws DateTimeException if the period cannot be calculated
* @throws ArithmeticException if numeric overflow occurs
*/
public abstract ChronoPeriod until(ChronoLocalDate endDateExclusive);
/**
* Formats this date using the specified formatter.
* <p>
* This date will be passed to the formatter to produce a string.
* <p>
* The default implementation must behave as follows:
* <pre>
* return formatter.format(this);
* </pre>
*
* @param formatter the formatter to use, not null
* @return the formatted date string, not null
* @throws DateTimeException if an error occurs during printing
*/
public String format(DateTimeFormatter formatter) {
Jdk8Methods.requireNonNull(formatter, "formatter");
return formatter.format(this);
}
//-----------------------------------------------------------------------
/**
* Combines this date with a time to create a {@code ChronoLocalDateTime}.
* <p>
* This returns a {@code ChronoLocalDateTime} formed from this date at the specified time.
* All possible combinations of date and time are valid.
*
* @param localTime the local time to use, not null
* @return the local date-time formed from this date and the specified time, not null
*/
public ChronoLocalDateTime<?> atTime(LocalTime localTime) {
return ChronoLocalDateTimeImpl.of(this, localTime);
}
//-----------------------------------------------------------------------
/**
* Converts this date to the Epoch Day.
* <p>
* The {@link ChronoField#EPOCH_DAY Epoch Day count} is a simple
* incrementing count of days where day 0 is 1970-01-01 (ISO).
* This definition is the same for all chronologies, enabling conversion.
*
* @return the Epoch Day equivalent to this date
*/
public long toEpochDay() {
return getLong(EPOCH_DAY);
}
//-----------------------------------------------------------------------
/**
* Compares this date to another date, including the chronology.
* <p>
* The comparison is based first on the underlying time-line date, then
* on the chronology.
* It is "consistent with equals", as defined by {@link Comparable}.
* <p>
* For example, the following is the comparator order:
* <ol>
* <li>{@code 2012-12-03 (ISO)}</li>
* <li>{@code 2012-12-04 (ISO)}</li>
* <li>{@code 2555-12-04 (ThaiBuddhist)}</li>
* <li>{@code 2012-12-05 (ISO)}</li>
* </ol>
* Values #2 and #3 represent the same date on the time-line.
* When two values represent the same date, the chronology ID is compared to distinguish them.
* This step is needed to make the ordering "consistent with equals".
* <p>
* If all the date objects being compared are in the same chronology, then the
* additional chronology stage is not required and only the local date is used.
* To compare the dates of two {@code TemporalAccessor} instances, including dates
* in two different chronologies, use {@link ChronoField#EPOCH_DAY} as a comparator.
*
* @param other the other date to compare to, not null
* @return the comparator value, negative if less, positive if greater
*/
@Override
public int compareTo(ChronoLocalDate other) {
int cmp = Jdk8Methods.compareLongs(toEpochDay(), other.toEpochDay());
if (cmp == 0) {
cmp = getChronology().compareTo(other.getChronology());
}
return cmp;
}
//-----------------------------------------------------------------------
/**
* Checks if this date is after the specified date ignoring the chronology.
* <p>
* This method differs from the comparison in {@link #compareTo} in that it
* only compares the underlying date and not the chronology.
* This allows dates in different calendar systems to be compared based
* on the time-line position.
* This is equivalent to using {@code date1.toEpochDay() > date2.toEpochDay()}.
*
* @param other the other date to compare to, not null
* @return true if this is after the specified date
*/
public boolean isAfter(ChronoLocalDate other) {
return this.toEpochDay() > other.toEpochDay();
}
/**
* Checks if this date is before the specified date ignoring the chronology.
* <p>
* This method differs from the comparison in {@link #compareTo} in that it
* only compares the underlying date and not the chronology.
* This allows dates in different calendar systems to be compared based
* on the time-line position.
* This is equivalent to using {@code date1.toEpochDay() < date2.toEpochDay()}.
*
* @param other the other date to compare to, not null
* @return true if this is before the specified date
*/
public boolean isBefore(ChronoLocalDate other) {
return this.toEpochDay() < other.toEpochDay();
}
/**
* Checks if this date is equal to the specified date ignoring the chronology.
* <p>
* This method differs from the comparison in {@link #compareTo} in that it
* only compares the underlying date and not the chronology.
* This allows dates in different calendar systems to be compared based
* on the time-line position.
* This is equivalent to using {@code date1.toEpochDay() == date2.toEpochDay()}.
*
* @param other the other date to compare to, not null
* @return true if the underlying date is equal to the specified date
*/
public boolean isEqual(ChronoLocalDate other) {
return this.toEpochDay() == other.toEpochDay();
}
//-----------------------------------------------------------------------
/**
* Checks if this date is equal to another date, including the chronology.
* <p>
* Compares this date with another ensuring that the date and chronology are the same.
* <p>
* To compare the dates of two {@code TemporalAccessor} instances, including dates
* in two different chronologies, use {@link ChronoField#EPOCH_DAY} as a comparator.
*
* @param obj the object to check, null returns false
* @return true if this is equal to the other date
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj instanceof ChronoLocalDate) {
return compareTo((ChronoLocalDate) obj) == 0;
}
return false;
}
/**
* A hash code for this date.
*
* @return a suitable hash code
*/
@Override
public int hashCode() {
long epDay = toEpochDay();
return getChronology().hashCode() ^ ((int) (epDay ^ (epDay >>> 32)));
}
//-----------------------------------------------------------------------
/**
* Outputs this date as a {@code String}.
* <p>
* The output will include the full local date and the chronology ID.
*
* @return the formatted date, not null
*/
@Override
public String toString() {
// getLong() reduces chances of exceptions in toString()
long yoe = getLong(YEAR_OF_ERA);
long moy = getLong(MONTH_OF_YEAR);
long dom = getLong(DAY_OF_MONTH);
StringBuilder buf = new StringBuilder(30);
buf.append(getChronology().toString())
.append(" ")
.append(getEra())
.append(" ")
.append(yoe)
.append(moy < 10 ? "-0" : "-").append(moy)
.append(dom < 10 ? "-0" : "-").append(dom);
return buf.toString();
}
}