{@inheritDoc} @throws DateTimeException {@inheritDoc} @throws ArithmeticException {@inheritDoc}
{@inheritDoc} @throws DateTimeException {@inheritDoc} @throws UnsupportedTemporalTypeException {@inheritDoc} @throws ArithmeticException {@inheritDoc}
Adjusts the specified temporal object to have the same date as this object. !(p) This returns a temporal object of the same observable type as the input with the date changed to be the same as this. !(p) The adjustment is equivalent to using {@link Temporal#_with(TemporalField, long)} passing {@link ChronoField#EPOCH_DAY} as the field. !(p) In most cases, it is clearer to reverse the calling pattern by using {@link Temporal#_with(TemporalAdjuster)}: !(pre) // these two lines are equivalent, but the second approach is recommended temporal = thisLocalDate.adjustInto(temporal); temporal = temporal._with(thisLocalDate); </pre> !(p) This instance is immutable and unaffected by this method call.
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.
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. !(p) This implementation performs the comparison defined above.
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.
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() == SomeChrono.ERA_NAME)}. !(p) This implementation uses {@link Chronology#eraOf(int)}.
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()}. !(p) This implementation performs the comparison based on the epoch-day.
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()}. !(p) This implementation performs the comparison based on the epoch-day.
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()}. !(p) This implementation performs the comparison based on the epoch-day.
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) This implementation uses {@link Chronology#isLeapYear(long)}.
Checks if the specified field is supported. !(p) This checks if the specified field can be queried on this date. If false, then calling the {@link #range(TemporalField) range}, {@link #get(TemporalField) get} and {@link #_with(TemporalField, long)} methods will throw an exception. !(p) The set of supported fields is defined by the chronology and normally includes all {@code ChronoField} date fields. !(p) If the field is not a {@code ChronoField}, then the result of this method is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)} passing {@code this} as the argument. Whether the field is supported is determined by the field.
Checks if the specified unit is supported. !(p) This checks if the specified unit can be added to or subtracted from this date. If false, then calling the {@link #plus(long, TemporalUnit)} and {@link #minus(long, TemporalUnit) minus} methods will throw an exception. !(p) The set of supported units is defined by the chronology and normally includes all {@code ChronoUnit} date units except {@code FOREVER}. !(p) If the unit is not a {@code ChronoUnit}, then the result of this method is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)} passing {@code this} as the argument. Whether the unit is supported is determined by the unit.
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.
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 implementation uses {@link #isLeapYear()} and returns 365 or 366.
{@inheritDoc} @throws DateTimeException {@inheritDoc} @throws ArithmeticException {@inheritDoc}
{@inheritDoc} @throws DateTimeException {@inheritDoc} @throws UnsupportedTemporalTypeException {@inheritDoc} @throws ArithmeticException {@inheritDoc}
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.
{@inheritDoc} @throws DateTimeException {@inheritDoc} @throws ArithmeticException {@inheritDoc}
{@inheritDoc} @throws DateTimeException {@inheritDoc} @throws ArithmeticException {@inheritDoc}
Queries this date using the specified query. !(p) This queries this date using the specified query strategy object. The {@code TemporalQuery} object defines the logic to be used to obtain the result. Read the documentation of the query to understand what the result of this method will be. !(p) The result of this method is obtained by invoking the {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the specified query passing {@code this} as the argument.
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. !(p) This implementation queries the {@code EPOCH_DAY} field.
A hash code for this date.
Outputs this date as a {@code string}. !(p) The output will include the full local date.
Calculates the amount of time until another date _in terms of the specified unit. !(p) This calculates the amount of time between two {@code ChronoLocalDate} objects _in terms of a single {@code TemporalUnit}. 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 {@code Temporal} passed to this method is converted to a {@code ChronoLocalDate} using {@link Chronology#date(TemporalAccessor)}. The calculation returns a whole number, representing the number of complete units between the two dates. For example, the amount _in days between two dates can be calculated using {@code startDate.until(endDate, DAYS)}. !(p) There are two equivalent ways of using this method. The first is to invoke this method. The second is to use {@link TemporalUnit#between(Temporal, Temporal)}: !(pre) // these two lines are equivalent amount = start.until(end, MONTHS); amount = MONTHS.between(start, end); </pre> The choice should be made based on which makes the code more readable. !(p) The calculation is implemented _in this method for {@link ChronoUnit}. The units {@code DAYS}, {@code WEEKS}, {@code MONTHS}, {@code YEARS}, {@code DECADES}, {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS} should be supported by all implementations. Other {@code ChronoUnit} values will throw an exception. !(p) If the unit is not a {@code ChronoUnit}, then the result of this method is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)} passing {@code this} as the first argument and the converted input temporal as the second argument. !(p) This instance is immutable and unaffected by this method call.
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.
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}.
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.
Checks if the specified unit is supported. !(p) This checks if the specified unit can be added to, or subtracted from, this date-time. If false, then calling the {@link #plus(long, TemporalUnit)} and {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
Returns an adjusted object of the same type as this object with the adjustment made. !(p) This adjusts this date-time according to the rules of the specified adjuster. A simple adjuster might simply set the one of the fields, such as the year field. A more complex adjuster might set the date to the last day of the month. A selection of common adjustments is provided _in {@link hunt.time.temporal.TemporalAdjusters TemporalAdjusters}. These include finding the "last day of the month" and "next Wednesday". The adjuster is responsible for handling special cases, such as the varying lengths of month and leap years. !(p) Some example code indicating how and why this method is used: !(pre) date = date._with(Month.JULY); // most key classes implement TemporalAdjuster date = date._with(lastDayOfMonth()); // static import from Adjusters date = date._with(next(WEDNESDAY)); // static import from Adjusters and DayOfWeek </pre>
Returns an object of the same type as this object with the specified field altered. !(p) This returns a new object based on this one with the value for the specified field changed. For example, on a {@code LocalDate}, this could be used to set the year, month or day-of-month. The returned object will have the same observable type as this object. !(p) In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st January, then changing the month to February would be unclear. In cases like this, the field is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February _in this example.
Returns an object of the same type as this object with an amount added. !(p) This adjusts this temporal, adding according to the rules of the specified amount. The amount is typically a {@link hunt.time.Period} but may be any other type implementing the {@link TemporalAmount} interface, such as {@link hunt.time.Duration}. !(p) Some example code indicating how and why this method is used: !(pre) date = date.plus(period); // add a Period instance date = date.plus(duration); // add a Duration instance date = date.plus(workingDays(6)); // example user-written workingDays method </pre> !(p) Note that calling {@code plus} followed by {@code minus} is not guaranteed to return the same date-time.
Returns an object of the same type as this object with the specified period added. !(p) This method returns a new object based on this one with the specified period added. For example, on a {@code LocalDate}, this could be used to add a number of years, months or days. The returned object will have the same observable type as this object. !(p) In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st January, then adding one month would be unclear. In cases like this, the field is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February _in this example.
Returns an object of the same type as this object with an amount subtracted. !(p) This adjusts this temporal, subtracting according to the rules of the specified amount. The amount is typically a {@link hunt.time.Period} but may be any other type implementing the {@link TemporalAmount} interface, such as {@link hunt.time.Duration}. !(p) Some example code indicating how and why this method is used: !(pre) date = date.minus(period); // subtract a Period instance date = date.minus(duration); // subtract a Duration instance date = date.minus(workingDays(6)); // example user-written workingDays method </pre> !(p) Note that calling {@code plus} followed by {@code minus} is not guaranteed to return the same date-time.
Returns an object of the same type as this object with the specified period subtracted. !(p) This method returns a new object based on this one with the specified period subtracted. For example, on a {@code LocalDate}, this could be used to subtract a number of years, months or days. The returned object will have the same observable type as this object. !(p) In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st March, then subtracting one month would be unclear. In cases like this, the field is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February _in this example.
Calculates the amount of time until another temporal _in terms of the specified unit. !(p) This calculates the amount of time between two temporal objects _in terms of a single {@code TemporalUnit}. The start and end points are {@code this} and the specified temporal. The end point is converted to be of the same type as the start point if different. The result will be negative if the end is before the start. For example, the amount _in hours between two temporal objects can be calculated using {@code startTime.until(endTime, HOURS)}. !(p) The calculation returns a whole number, representing the number of complete units between the two temporals. For example, the amount _in hours between the times 11:30 and 13:29 will only be one hour as it is one minute short of two hours. !(p) There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use {@link TemporalUnit#between(Temporal, Temporal)}: !(pre) // these two lines are equivalent temporal = start.until(end, unit); temporal = unit.between(start, end); </pre> The choice should be made based on which makes the code more readable. !(p) For example, this method allows the number of days between two dates to be calculated: !(pre) long daysBetween = start.until(end, DAYS); // or alternatively long daysBetween = DAYS.between(start, end); </pre>
Adjusts the specified temporal object. !(p) This adjusts the specified temporal object using the logic encapsulated _in the implementing class. Examples might be an adjuster that sets the date avoiding weekends, or one that sets the date to the last day of the month. !(p) There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use {@link Temporal#_with(TemporalAdjuster)}: !(pre) // these two lines are equivalent, but the second approach is recommended temporal = thisAdjuster.adjustInto(temporal); temporal = temporal._with(thisAdjuster); </pre> It is recommended to use the second approach, {@code _with(TemporalAdjuster)}, as it is a lot clearer to read _in code.
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.
!(h3)When to use this interface</h3> 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. !(p) This concept can seem surprising at first, as the natural way to globalize an application might initially appear to be to abstract the calendar system. However, as explored below, abstracting the calendar system is usually the wrong approach, resulting _in logic errors and hard to find bugs. As such, it should be considered an application-wide architectural decision to choose to use this interface as opposed to {@code LocalDate}.
!(h3)Architectural issues to consider</h3> 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.
!(h3)False assumptions causing bugs _in multi-calendar system code</h3> 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.
!(h3)Using LocalDate instead</h3> The primary alternative to using this interface throughout your application is as follows. !(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> 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: !(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> 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.
@implSpec 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.
@since 1.8