IChronoLocalDate Interface
Definition
Important
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A date without time-of-day or time-zone in an arbitrary chronology, intended for advanced globalization use cases.
[Android.Runtime.Register("java/time/chrono/ChronoLocalDate", "", "Java.Time.Chrono.IChronoLocalDateInvoker", ApiSince=26)]
public interface IChronoLocalDate : IDisposable, Java.Interop.IJavaPeerable, Java.Lang.IComparable, Java.Time.Temporal.ITemporal, Java.Time.Temporal.ITemporalAdjuster[<Android.Runtime.Register("java/time/chrono/ChronoLocalDate", "", "Java.Time.Chrono.IChronoLocalDateInvoker", ApiSince=26)>]
type IChronoLocalDate = interface
interface IComparable
interface IJavaObject
interface IDisposable
interface IJavaPeerable
interface ITemporal
interface ITemporalAccessor
interface ITemporalAdjuster- Derived
- Attributes
- Implements
Remarks
A date without time-of-day or time-zone in an arbitrary chronology, intended for advanced globalization use cases.
<b>Most applications should declare method signatures, fields and variables as LocalDate, not this interface.</b>
A ChronoLocalDate is the abstract representation of a date where the Chronology chronology, or calendar system, is pluggable. The date is defined in terms of fields expressed by TemporalField, where most common implementations are defined in ChronoField. The chronology defines how the calendar system operates and the meaning of the standard fields.
<h2>When to use this interface</h2> The design of the API encourages the use of LocalDate rather than this interface, even in the case where the application needs to deal with multiple calendar systems.
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 LocalDate.
<h3>Architectural issues to consider</h3> These are some of the points that must be considered before using this interface throughout an application.
1) Applications using this interface, as opposed to using just 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.
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 ChronoLocalDate could therefore be passed a poorly or maliciously written mutable implementation.
3) Applications using this interface must consider the impact of eras. LocalDate shields users from the concept of eras, by ensuring that getYear() returns the proleptic year. That decision ensures that developers can think of 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.
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.
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.
6) Most of the time, passing a 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.
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.
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.
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.
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.
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.
Code that assumes that because the year of date1 is greater than the year of date2 then date1 is after 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.
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.
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 LocalDate. <li>Either store the chronology (calendar system) in the user profile or lookup the chronology from the user locale <li>Convert the ISO 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.
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.
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.
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 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 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 TemporalAccessor if read-only access is required, or use Temporal if read-write access is required.
Added in 1.8.
Java documentation for java.time.chrono.ChronoLocalDate.
Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.
Properties
| Chronology | |
| Era |
Gets the era, as defined by the chronology. |
| Handle |
Gets the JNI value of the underlying Android object. (Inherited from IJavaObject) |
| IsLeapYear |
Checks if the year is a leap year, as defined by the calendar system. |
| JniIdentityHashCode |
Returns the value of |
| JniManagedPeerState |
State of the managed peer. (Inherited from IJavaPeerable) |
| JniPeerMembers |
Member access and invocation support. (Inherited from IJavaPeerable) |
| PeerReference |
Returns a JniObjectReference of the wrapped Java object instance. (Inherited from IJavaPeerable) |
Methods
| AdjustInto(ITemporal) |
Adjusts the specified temporal object. (Inherited from ITemporalAdjuster) |
| AtTime(LocalTime) |
Combines this date with a time to create a |
| CompareTo(IChronoLocalDate) |
Compares this date to another date, including the chronology. |
| CompareTo(Object) |
Compares this object with the specified object for order. (Inherited from IComparable) |
| Disposed() |
Called when the instance has been disposed. (Inherited from IJavaPeerable) |
| DisposeUnlessReferenced() |
If there are no outstanding references to this instance, then
calls |
| Equals(Object) |
Checks if this date is equal to another date, including the chronology. |
| Finalized() |
Called when the instance has been finalized. (Inherited from IJavaPeerable) |
| Format(DateTimeFormatter) |
Formats this date using the specified formatter. |
| From(ITemporalAccessor) |
Obtains an instance of |
| Get(ITemporalField) |
Gets the value of the specified field as an |
| GetHashCode() |
A hash code for this date. |
| GetLong(ITemporalField) |
Gets the value of the specified field as a |
| IsAfter(IChronoLocalDate) |
Checks if this date is after the specified date ignoring the chronology. |
| IsBefore(IChronoLocalDate) |
Checks if this date is before the specified date ignoring the chronology. |
| IsEqual(IChronoLocalDate) |
Checks if this date is equal to the specified date ignoring the chronology. |
| IsSupported(ITemporalField) |
Checks if the specified field is supported. (Inherited from ITemporalAccessor) |
| IsSupported(ITemporalUnit) |
Checks if the specified unit is supported. (Inherited from ITemporal) |
| LengthOfMonth() |
Returns the length of the month represented by this date, as defined by the calendar system. |
| LengthOfYear() |
Returns the length of the year represented by this date, as defined by the calendar system. |
| Minus(Int64, ITemporalUnit) |
Returns an object of the same type as this object with the specified period subtracted. (Inherited from ITemporal) |
| Minus(ITemporalAmount) |
Returns an object of the same type as this object with an amount subtracted. (Inherited from ITemporal) |
| Plus(Int64, ITemporalUnit) |
Returns an object of the same type as this object with the specified period added. (Inherited from ITemporal) |
| Plus(ITemporalAmount) |
Returns an object of the same type as this object with an amount added. (Inherited from ITemporal) |
| Query(ITemporalQuery) |
Queries this date-time. (Inherited from ITemporalAccessor) |
| Range(ITemporalField) |
Gets the range of valid values for the specified field. (Inherited from ITemporalAccessor) |
| SetJniIdentityHashCode(Int32) |
Set the value returned by |
| SetJniManagedPeerState(JniManagedPeerStates) | (Inherited from IJavaPeerable) |
| SetPeerReference(JniObjectReference) |
Set the value returned by |
| TimeLineOrder() |
Gets a comparator that compares |
| ToEpochDay() |
Converts this date to the Epoch Day. |
| ToString() |
Outputs this date as a |
| UnregisterFromRuntime() |
Unregister this instance so that the runtime will not return it from future Java.Interop.JniRuntime+JniValueManager.PeekValue invocations. (Inherited from IJavaPeerable) |
| Until(IChronoLocalDate) |
Calculates the period between this date and another date as a |
| Until(ITemporal, ITemporalUnit) |
Calculates the amount of time until another date in terms of the specified unit. |
| With(ITemporalAdjuster) |
Returns an adjusted object of the same type as this object with the adjustment made. (Inherited from ITemporal) |
| With(ITemporalField, Int64) |
Returns an object of the same type as this object with the specified field altered. (Inherited from ITemporal) |
Explicit Interface Implementations
| ITemporal.IsSupported(ITemporalUnit) |
Checks if the specified unit is supported. |
| ITemporal.Minus(Int64, ITemporalUnit) |
To be added |
| ITemporal.Minus(ITemporalAmount) |
To be added |
| ITemporal.Plus(Int64, ITemporalUnit) |
To be added |
| ITemporal.Plus(ITemporalAmount) |
To be added |
| ITemporal.With(ITemporalAdjuster) |
To be added |
| ITemporal.With(ITemporalField, Int64) |
To be added |
| ITemporalAccessor.IsSupported(ITemporalField) |
Checks if the specified field is supported. |
| ITemporalAccessor.Query(ITemporalQuery) |
Queries this date using the specified query. |
| ITemporalAdjuster.AdjustInto(ITemporal) |
Adjusts the specified temporal object to have the same date as this object. |
Extension Methods
| JavaCast<TResult>(IJavaObject) |
Performs an Android runtime-checked type conversion. |
| JavaCast<TResult>(IJavaObject) | |
| GetJniTypeName(IJavaPeerable) | |