1 /*
   2  * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /*
  27  * This file is available under and governed by the GNU General Public
  28  * License version 2 only, as published by the Free Software Foundation.
  29  * However, the following notice accompanied the original version of this
  30  * file:
  31  *
  32  * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
  33  *
  34  * All rights reserved.
  35  *
  36  * Redistribution and use in source and binary forms, with or without
  37  * modification, are permitted provided that the following conditions are met:
  38  *
  39  *  * Redistributions of source code must retain the above copyright notice,
  40  *    this list of conditions and the following disclaimer.
  41  *
  42  *  * Redistributions in binary form must reproduce the above copyright notice,
  43  *    this list of conditions and the following disclaimer in the documentation
  44  *    and/or other materials provided with the distribution.
  45  *
  46  *  * Neither the name of JSR-310 nor the names of its contributors
  47  *    may be used to endorse or promote products derived from this software
  48  *    without specific prior written permission.
  49  *
  50  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  51  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  52  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  53  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  54  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  55  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  56  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  57  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  58  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  59  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  60  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  61  */
  62 
  63 /**
  64  * <p>
  65  * Access to date and time using fields and units, and date time adjusters.
  66  * </p>
  67  * <p>
  68  * This package expands on the base package to provide additional functionality for
  69  * more powerful use cases. Support is included for:
  70  * </p>
  71  * <ul>
  72  * <li>Units of date-time, such as years, months, days and hours</li>
  73  * <li>Fields of date-time, such as month-of-year, day-of-week or hour-of-day</li>
  74  * <li>Date-time adjustment functions</li>
  75  * <li>Different definitions of weeks</li>
  76  * </ul>
  77  *
  78  * <h3>Fields and Units</h3>
  79  * <p>
  80  * Dates and times are expressed in terms of fields and units.
  81  * A unit is used to measure an amount of time, such as years, days or minutes.
  82  * All units implement {@link java.time.temporal.TemporalUnit}.
  83  * The set of well known units is defined in {@link java.time.temporal.ChronoUnit}, such as {@code DAYS}.
  84  * The unit interface is designed to allow applications defined units.
  85  * </p>
  86  * <p>
  87  * A field is used to express part of a larger date-time, such as year, month-of-year or second-of-minute.
  88  * All fields implement {@link java.time.temporal.TemporalField}.
  89  * The set of well known fields are defined in {@link java.time.temporal.ChronoField}, such as {@code HOUR_OF_DAY}.
  90  * Additional fields are defined by {@link java.time.temporal.JulianFields}, {@link java.time.temporal.WeekFields}
  91  * and {@link java.time.temporal.IsoFields}.
  92  * The field interface is designed to allow applications defined fields.
  93  * </p>
  94  * <p>
  95  * This package provides tools that allow the units and fields of date and time to be accessed
  96  * in a general way most suited for frameworks.
  97  * {@link java.time.temporal.Temporal} provides the abstraction for date time types that support fields.
  98  * Its methods support getting the value of a field, creating a new date time with the value of
  99  * a field modified, and querying for additional information, typically used to extract the offset or time-zone.
 100  * </p>
 101  * <p>
 102  * One use of fields in application code is to retrieve fields for which there is no convenience method.
 103  * For example, getting the day-of-month is common enough that there is a method on {@code LocalDate}
 104  * called {@code getDayOfMonth()}. However for more unusual fields it is necessary to use the field.
 105  * For example, {@code date.get(ChronoField.ALIGNED_WEEK_OF_MONTH)}.
 106  * The fields also provide access to the range of valid values.
 107  * </p>
 108  *
 109  * <h3>Adjustment and Query</h3>
 110  * <p>
 111  * A key part of the date-time problem space is adjusting a date to a new, related value,
 112  * such as the "last day of the month", or "next Wednesday".
 113  * These are modeled as functions that adjust a base date-time.
 114  * The functions implement {@link java.time.temporal.TemporalAdjuster} and operate on {@code Temporal}.
 115  * A set of common functions are provided in {@link java.time.temporal.Adjusters}.
 116  * For example, to find the first occurrence of a day-of-week after a given date, use
 117  * {@link java.time.temporal.Adjusters#next(DayOfWeek)}, such as
 118  * {@code date.with(next(MONDAY))}.
 119  * Applications can also define adjusters by implementing {@code TemporalAdjuster}.
 120  * </p>
 121  * <p>
 122  * The {@link java.time.temporal.TemporalAmount} interface models amounts of relative time.
 123  * </p>
 124  * <p>
 125  * In addition to adjusting a date-time, an interface is provided to enable querying -
 126  * {@link java.time.temporal.TemporalQuery}.
 127  * The most common implementations of the query interface are method references.
 128  * The {@code from(TemporalAccessor)} methods on major classes can all be used, such as
 129  * {@code LocalDate::from} or {@code Month::from}.
 130  * Further implementations are provided in {@link java.time.temporal.Queries}.
 131  * Applications can also define queries by implementing {@code TemporalQuery}.
 132  * </p>
 133  *
 134  * <h3>Weeks</h3>
 135  * <p>
 136  * Different locales have different definitions of the week.
 137  * For example, in Europe the week typically starts on a Monday, while in the US it starts on a Sunday.
 138  * The {@link java.time.temporal.WeekFields} class models this distinction.
 139  * </p>
 140  * <p>
 141  * The ISO calendar system defines an additional week-based division of years.
 142  * This defines a year based on whole Monday to Monday weeks.
 143  * This is modeled in {@link java.time.temporal.IsoFields}.
 144  * </p>
 145  *
 146  * <h3>Package specification</h3>
 147  * <p>
 148  * Unless otherwise noted, passing a null argument to a constructor or method in any class or interface
 149  * in this package will cause a {@link java.lang.NullPointerException NullPointerException} to be thrown.
 150  * The Javadoc "@param" definition is used to summarise the null-behavior.
 151  * The "@throws {@link java.lang.NullPointerException}" is not explicitly documented in each method.
 152  * </p>
 153  * <p>
 154  * All calculations should check for numeric overflow and throw either an {@link java.lang.ArithmeticException}
 155  * or a {@link java.time.DateTimeException}.
 156  * </p>
 157  * @since JDK1.8
 158  */
 159 package java.time.temporal;