Package org.joda.time

Provides support for dates, times, time zones, durations, intervals, and partials.

See:
          Description

Interface Summary
DateTimeUtils.MillisProvider A millisecond provider, allowing control of the system clock.
ReadableDateTime Defines an instant in time that can be queried using datetime fields.
ReadableDuration Defines an exact duration of time in milliseconds.
ReadableInstant Defines an instant in the datetime continuum.
ReadableInterval Readable interface for an interval of time between two instants.
ReadablePartial Defines a partial time that does not support every datetime field, and is thus a local time.
ReadablePeriod Defines a time period specified in terms of individual duration fields such as years and days.
ReadWritableDateTime Defines an instant in time that can be queried and modified using datetime fields.
ReadWritableInstant Defines an instant in the datetime continuum that can be queried and modified.
ReadWritableInterval Writable interface for an interval.
ReadWritablePeriod Defines a duration of time that can be queried and modified using datetime fields.
 

Class Summary
Chronology Chronology provides access to the individual date time fields for a chronological calendar system.
DateMidnight Deprecated. The time of midnight does not exist in some time zones where the daylight saving time forward shift skips the midnight hour.
DateMidnight.Property DateMidnight.Property binds a DateMidnight to a DateTimeField allowing powerful datetime functionality to be easily accessed.
DateTime DateTime is the standard implementation of an unmodifiable datetime class.
DateTime.Property DateTime.Property binds a DateTime to a DateTimeField allowing powerful datetime functionality to be easily accessed.
DateTimeComparator DateTimeComparator provides comparators to compare one date with another.
DateTimeConstants DateTimeConstants is a non-instantiable class of constants used in the date time system.
DateTimeField Defines the calculation engine for date and time fields.
DateTimeFieldType Identifies a field, such as year or minuteOfHour, in a chronology-neutral way.
DateTimeUtils DateTimeUtils provide public utility methods for the date-time library.
DateTimeZone DateTimeZone represents a time zone.
Days An immutable time period representing a number of days.
Duration An immutable duration specifying a length of time in milliseconds.
DurationField Defines the calculation engine for duration fields.
DurationFieldType Identifies a duration field, such as years or minutes, in a chronology-neutral way.
Hours An immutable time period representing a number of hours.
Instant Instant is the standard implementation of a fully immutable instant in time.
Interval Interval is the standard implementation of an immutable time interval.
JodaTimePermission JodaTimePermission is used for securing global method calls in the Joda-Time library.
LocalDate LocalDate is an immutable datetime class representing a date without a time zone.
LocalDate.Property LocalDate.Property binds a LocalDate to a DateTimeField allowing powerful datetime functionality to be easily accessed.
LocalDateTime LocalDateTime is an unmodifiable datetime class representing a datetime without a time zone.
LocalDateTime.Property LocalDateTime.Property binds a LocalDateTime to a DateTimeField allowing powerful datetime functionality to be easily accessed.
LocalTime LocalTime is an immutable time class representing a time without a time zone.
LocalTime.Property LocalTime.Property binds a LocalTime to a DateTimeField allowing powerful datetime functionality to be easily accessed.
Minutes An immutable time period representing a number of minutes.
MonthDay MonthDay is an immutable partial supporting the monthOfYear and dayOfMonth fields.
MonthDay.Property The property class for MonthDay.
Months An immutable time period representing a number of months.
MutableDateTime MutableDateTime is the standard implementation of a modifiable datetime class.
MutableDateTime.Property MutableDateTime.Property binds a MutableDateTime to a DateTimeField allowing powerful datetime functionality to be easily accessed.
MutableInterval MutableInterval is the standard implementation of a mutable time interval.
MutablePeriod Standard mutable time period implementation.
Partial Partial is an immutable partial datetime supporting any set of datetime fields.
Partial.Property The property class for Partial.
Period An immutable time period specifying a set of duration field values.
PeriodType Controls a period implementation by specifying which duration fields are to be used.
Seconds An immutable time period representing a number of seconds.
TimeOfDay Deprecated. Use LocalTime which has a much better internal implementation and has been available since 1.3
TimeOfDay.Property Deprecated. Use LocalTime which has a much better internal implementation
Weeks An immutable time period representing a number of weeks.
YearMonth YearMonth is an immutable partial supporting the year and monthOfYear fields.
YearMonth.Property The property class for YearMonth.
YearMonthDay Deprecated. Use LocalDate which has a much better internal implementation and has been available since 1.3
YearMonthDay.Property Deprecated. Use LocalDate which has a much better internal implementation
Years An immutable time period representing a number of years.
 

Exception Summary
IllegalFieldValueException Exception thrown when attempting to set a field outside its supported range.
IllegalInstantException Exception thrown when attempting to create an instant or date-time that cannot exist.
 

Package org.joda.time Description

Provides support for dates, times, time zones, durations, intervals, and partials. This package aims to fully replace the Java Date, Calendar, and TimeZone classes. This implementation covers both the Gregorian/Julian calendar system and the ISO8601 standard. Additional calendar systems and extensions can be created as well.

The ISO8601 standard is the international standard for dates, times, durations, and intervals. It defines text representations, the first day of the week as Monday, and the first week in a year as having a Thursday in it. This standard is being increasingly used in computer interchange and is the agreed format for XML. For most uses, the ISO standard is the same as Gregorian, and is thus the preferred format.

Interfaces

The main API concepts are defined by interfaces:

These define the public interface to dates, times, periods, intervals and durations. As with java.util.Date and Calendar, the design is millisecond based with an epoch of 1970-01-01. This should enable easy conversions.

Implementations

The basic implementation of the ReadableInstant interface is Instant. This is a simple immutable class that stores the millisecond value and integrates with Java Date and Calendar. The class follows the definition of the millisecond instant fully, thus it references the ISO8601 calendar system and UTC time zone. If you are dealing with an instant in time but do not know, or do not want to specify, which calendar system it refers to, then you should use this class.

The main implementation class for datetimes is the DateTime class. This implements the ReadableDateTime interface, providing convenient methods to access the fields of the datetime. Conversion methods allow integration with the Java Date and Calendar classes.

Like Instant, DateTime is immutable, and it can be used safely in a multi-threaded environment. In order to be fully immutable, key clases are declared as final. Abstract superclasses are provided should you need to define your own implementations.

The concrete implementations of the ReadWritable... interfaces are named the same as their immutable counterparts, but with a "Mutable" prefix. For example, MutableDateTime implements ReadWritableDateTime, making datetime editing easy. Note that it is possible to use the immutable DateTime for modifying datetimes, however each modification method returns a new instance of DateTime.

Interface usage

The interfaces in Joda-Time are not designed to operate in the same way as those in the Java Collections Framework (List/Map/Set etc). The Joda-Time interfaces represent a core subset of the functionality available via the actual classes. Thus, much of the work of an application will probably use methods on the class, not on the interface. Your application must determine whether it should define dates in terms of the interfaces, or in terms of the classes.

The interfaces provide simple methods to access an instance of the immutable class, which is implemented either via typecast or object creation. Thus, if you hold a reference to a ReadableInstant, and you call the method toDateTime(), the same instance will be returned (typecast) if it already was a DateTime.

Chronologies and Fields

In order to enable the package to be easily extended, each field of the datetime, such as the month, is calculated by an implementation of DateTimeField. Likewise, duration fields are calculated by specialized DurationField instances. If desired, users can write their own implementations to retrieve an unusual field from the millisecond value.

The datetime and duration fields that together represent a calendar system are grouped into a Chronology. The chronology represents all the information to convert from a millisecond value to human understandable fields in a specific calendar system. Chronologies are provided for ISO, Gregorian/Julian (GJ), Buddhist, Coptic and Ethiopic. More implementations are sought from the community.

The chronology and field classes are singletons. This design results in a low overhead on the date and time classes. The Java Calendar class performs poorly because it has many internal fields that are constantly kept in sync. This design only calculates fields when required, resulting in lightweight and simple date time classes.

When reviewing the library for the first time, it is easy to mistake the number of classes with complexity. The library is in fact clearly divided between user packages and implementation packages in the javadoc. Most users will should not need to be concerned with the back-end implementation.

Partials

Partials are like instants, except they do not completely specify a point in time. The main interface is ReadablePartial.

The main implementations are:

For consistency, the API of each partial class is similar to that of an instant class.

All partial implementations represent a local time, in other words without a time zone. Thus, to convert a partial to an instant (which does contain a time zone) requires adding a zone.

Formatting

Formatting is provided by the format subpackage. Comprehensive support is provided for outputting dates and times in multiple formats. A pattern similar to Java SimpleDateFormat can be used, but a more advanced programmatic technique is available via the builder classes.



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