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  * Copyright (c) 2008-2012, Stephen Colebourne & Michael Nascimento Santos
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 <body>
     <p>
         A new Date and Time API for Java.
         The design includes a relatively large number of classes and methods,
         however each follows a common design language, especially in method prefixes.
         Once the prefixes are understood, the API is relatively simple to comprehend.
     </p>
     <p>
         The Java Time API is composed of several packages, each with a primary function:
     </p>
     <p>
         {@link java.time} contains the main API based on the ISO-8601 standard.
         The classes defined here represent the principal date-time concepts,
         including instants, durations, dates, times, time-zones and periods.
         They are based on the ISO calendar system, which is the <i>de facto</i> world
         calendar following the proleptic Gregorian rules.
         All the classes are immutable and thread-safe.
     </p>
     <p>
         {@link java.time.temporal} contains the API for accessing the fields and units
         of date-time. Units are measurable, such as years, months and hours.
         For example, the expression "2 hours later" uses the hours unit.
         By contrast, fields are mini-calculations, defining a value.
         For example, month-of-year, day-of-week and hour-of-day are all fields.
         The set of supported units and fields can be extended by applications if desired.
     </p>
     <p>
         {@link java.time.format} contains the API to print and parse fields into date-time
         objects and to customize parsing and printing.
         Formatters can be created in a variety of ways, including constants, patterns,
         localized styles and a builder.
         Formatters are immutable and thread-safe.
     </p>
     <p>
         {@link java.time.zone} contains the API to handle time-zones.
         Detailed information is made available about the rules of each time-zone.
     </p>
     <p>
         {@link java.time.chrono} contains the basic part of the calendar neutral API
         and alternate calendar systems.
         This is intended for use by applications that need to use localized calendars.
         Support is provided for the Hijrah, Japanese, Minguo, and Thai Buddhist Calendars.
     </p>
     <h3>Design notes</h3>
     <p>
         Where possible, the API avoids the use of null.
         All methods define whether they accept or return null in the Javadoc.
         As a general rule, methods do not accept or return null.
         A key exception is any method that takes an object and returns a boolean, for the purpose
         of checking or validating, will generally return false for null.
     </p>
     <p>
         The API is designed to be type-safe where reasonable in the main high-level API.
         Thus, there are separate classes for the distinct concepts of date, time and date-time, plus variants
         for offset and time-zones. The core 7 date-time classes, plus Instant, handle the needs of most applications.
         Further classes handle other combinations - year, year-month and month-day in a type-safe manner.
     </p>
     <p>
         In a language like Java, the use of many different types tends to cause API bloat.
         This is handled here through the use of common method naming patterns throughout the API.
         The common prefixes are 'of', 'get', 'is', 'with', 'plus', 'minus', 'to' and 'at'.
         See {@link java.time.LocalDate} for an example of each of these methods.
     </p>
     <p>
         Following type-safety to its logical conclusion would result in more classes, especially for time -
         hour-minute, hour-minute-second and hour-minute-second-nanosecond.
         While logically pure, this was not possible in practice, as the additional classes would have
         excessively complicated the API. Notably, there would be additional combinations at the offset
         and date-time levels, such as offset-date-hour-minute.
         To avoid this explosion of types, {@link java.time.LocalTime} is used for all precisions of time.
         By contrast, some additional classes were used for dates, such as {@link java.time.YearMonth}.
         This proved necessary, as the API for year-month is significantly different to that for a date, whereas
         an absence of nanoseconds in a time can be approximated by returning zero.
     </p>
     <p>
         Similarly, full type-safety might argue for a separate class for each field in date-time,
         such as a class for HourOfDay and another for DayOfMonth.
         This approach was tried, but was excessively complicated in the Java language, lacking usability.
         A similar problem occurs with periods.
         There is a case for a separate class for each period unit, such as a type for Years and a type for Minutes.
         However, this yields a lot of classes and a problem of type conversion.
         As such, general access to fields and units is not wrapped in a class.
     </p>
     <p>
         Multiple calendar systems is an awkward addition to the design challenges.
         The first principal is that most users want the standard ISO calendar system.
         As such, the main classes are ISO-only. The second principal is that most of those that want a
         non-ISO calendar system want it for user interaction, thus it is a UI localization issue.
         As such, date and time objects should be held as ISO objects in the data model and persistent
         storage, only being converted to and from a local calendar for display.
         The calendar system would be stored separately in the user preferences.
     </p>
     <p>
         There are, however, some limited use cases where users believe they need to store and use
         dates in arbitrary calendar systems throughout the application.
         This is supported by {@link java.time.chrono.ChronoLocalDate}, however it is vital to read
         all the associated warnings in the Javadoc of that interface before using it.
         In summary, applications that require general interoperation between multiple calendar systems
         typically need to be written in a very different way to those only using the ISO calendar,
         thus most applications should just use ISO and avoid {@code ChronoLocalDate}.
     </p>
     <p>
         Throughout all of this, a key goal was to allow date-time fields and units to be defined by applications.
         This has been achieved having tried many different designs.
     </p>
 </body>
	<!--
	/*
	* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
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	/*
	* This file is available under and governed by the GNU General Public
	* License version 2 only, as published by the Free Software Foundation.
	* However, the following notice accompanied the original version of this
	* file:
	*
	* Copyright (c) 2008-2012, 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
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
	* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
	* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/
	-->
	<body>
	<p>
	A new Date and Time API for Java.
	The design includes a relatively large number of classes and methods,
	however each follows a common design language, especially in method prefixes.
	Once the prefixes are understood, the API is relatively simple to comprehend.
	</p>
	<p>
	The Java Time API is composed of several packages, each with a primary function:
	</p>
	<p>
	{@link java.time} contains the main API based on the ISO-8601 standard.
	The classes defined here represent the principal date-time concepts,
	including instants, durations, dates, times, time-zones and periods.
	They are based on the ISO calendar system, which is the <i>de facto</i> world
	calendar following the proleptic Gregorian rules.
	All the classes are immutable and thread-safe.
	</p>
	<p>
	{@link java.time.temporal} contains the API for accessing the fields and units
	of date-time. Units are measurable, such as years, months and hours.
	For example, the expression "2 hours later" uses the hours unit.
	By contrast, fields are mini-calculations, defining a value.
	For example, month-of-year, day-of-week and hour-of-day are all fields.
	The set of supported units and fields can be extended by applications if desired.
	</p>
	<p>
	{@link java.time.format} contains the API to print and parse fields into date-time
	objects and to customize parsing and printing.
	Formatters can be created in a variety of ways, including constants, patterns,
	localized styles and a builder.
	Formatters are immutable and thread-safe.
	</p>
	<p>
	{@link java.time.zone} contains the API to handle time-zones.
	Detailed information is made available about the rules of each time-zone.
	</p>
	<p>
	{@link java.time.chrono} contains the basic part of the calendar neutral API
	and alternate calendar systems.
	This is intended for use by applications that need to use localized calendars.
	Support is provided for the Hijrah, Japanese, Minguo, and Thai Buddhist Calendars.
	</p>
	<h3>Design notes</h3>
	<p>
	Where possible, the API avoids the use of null.
	All methods define whether they accept or return null in the Javadoc.
	As a general rule, methods do not accept or return null.
	A key exception is any method that takes an object and returns a boolean, for the purpose
	of checking or validating, will generally return false for null.
	</p>
	<p>
	The API is designed to be type-safe where reasonable in the main high-level API.
	Thus, there are separate classes for the distinct concepts of date, time and date-time, plus variants
	for offset and time-zones. The core 7 date-time classes, plus Instant, handle the needs of most applications.
	Further classes handle other combinations - year, year-month and month-day in a type-safe manner.
	</p>
	<p>
	In a language like Java, the use of many different types tends to cause API bloat.
	This is handled here through the use of common method naming patterns throughout the API.
	The common prefixes are 'of', 'get', 'is', 'with', 'plus', 'minus', 'to' and 'at'.
	See {@link java.time.LocalDate} for an example of each of these methods.
	</p>
	<p>
	Following type-safety to its logical conclusion would result in more classes, especially for time -
	hour-minute, hour-minute-second and hour-minute-second-nanosecond.
	While logically pure, this was not possible in practice, as the additional classes would have
	excessively complicated the API. Notably, there would be additional combinations at the offset
	and date-time levels, such as offset-date-hour-minute.
	To avoid this explosion of types, {@link java.time.LocalTime} is used for all precisions of time.
	By contrast, some additional classes were used for dates, such as {@link java.time.YearMonth}.
	This proved necessary, as the API for year-month is significantly different to that for a date, whereas
	an absence of nanoseconds in a time can be approximated by returning zero.
	</p>
	<p>
	Similarly, full type-safety might argue for a separate class for each field in date-time,
	such as a class for HourOfDay and another for DayOfMonth.
	This approach was tried, but was excessively complicated in the Java language, lacking usability.
	A similar problem occurs with periods.
	There is a case for a separate class for each period unit, such as a type for Years and a type for Minutes.
	However, this yields a lot of classes and a problem of type conversion.
	As such, general access to fields and units is not wrapped in a class.
	</p>
	<p>
	Multiple calendar systems is an awkward addition to the design challenges.
	The first principal is that most users want the standard ISO calendar system.
	As such, the main classes are ISO-only. The second principal is that most of those that want a
	non-ISO calendar system want it for user interaction, thus it is a UI localization issue.
	As such, date and time objects should be held as ISO objects in the data model and persistent
	storage, only being converted to and from a local calendar for display.
	The calendar system would be stored separately in the user preferences.
	</p>
	<p>
	There are, however, some limited use cases where users believe they need to store and use
	dates in arbitrary calendar systems throughout the application.
	This is supported by {@link java.time.chrono.ChronoLocalDate}, however it is vital to read
	all the associated warnings in the Javadoc of that interface before using it.
	In summary, applications that require general interoperation between multiple calendar systems
	typically need to be written in a very different way to those only using the ISO calendar,
	thus most applications should just use ISO and avoid {@code ChronoLocalDate}.
	</p>
	<p>
	Throughout all of this, a key goal was to allow date-time fields and units to be defined by applications.
	This has been achieved having tried many different designs.
	</p>
	</body>