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
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   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
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  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, 2013 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
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  60  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  61  */
  62 package java.time.temporal;
  63 
  64 import java.time.DateTimeException;
  65 import java.time.Duration;
  66 import java.time.Period;
  67 import java.util.List;
  68 
  69 /**
  70  * Framework-level interface defining an amount of time, such as
  71  * "6 hours", "8 days" or "2 years and 3 months".
  72  * <p>
  73  * This is the base interface type for amounts of time.
  74  * An amount is distinct from a date or time-of-day in that it is not tied
  75  * to any specific point on the time-line.
  76  * <p>
  77  * The amount can be thought of as a {@code Map} of {@link TemporalUnit} to
  78  * {@code long}, exposed via {@link #getUnits()}and {@link #get(TemporalUnit)}.
  79  * A simple case might have a single unit-value pair, such as "6 hours".
  80  * A more complex case may have multiple unit-value pairs, such as
  81  * "7 years, 3 months and 5 days".
  82  * <p>
  83  * There are two common implementations.
  84  * {@link Period} is a date-based implementation, storing years, months and days.
  85  * {@link Duration} is a time-based implementation, storing seconds and nanoseconds,
  86  * but providing some access using other duration based units such as minutes,
  87  * hours and fixed 24-hour days.
  88  * <p>
  89  * This interface is a framework-level interface that should not be widely
  90  * used in application code. Instead, applications should create and pass
  91  * around instances of concrete types, such as {@code Period} and {@code Duration}.
  92  *
  93  * <h3>Specification for implementors</h3>
  94  * This interface places no restrictions on the mutability of implementations,
  95  * however immutability is strongly recommended.
  96  *
  97  * @since 1.8
  98  */
  99 public interface TemporalAmount {
 100 
 101     /**
 102      * Returns the value of the requested unit.
 103      * The units returned from {@link #getUnits()} uniquely define the
 104      * value of the {@code TemporalAmount}.  A value must be returned
 105      * for each unit listed in {@code getUnits}.
 106      *
 107      * <h3>Specification for implementors</h3>
 108      * Implementations may declare support for units not listed by {@link #getUnits()}.
 109      * Typically, the implementation would define additional units
 110      * as conversions for the convenience of developers.
 111      *
 112      * @param unit the {@code TemporalUnit} for which to return the value
 113      * @return the long value of the unit
 114      * @throws DateTimeException if the {@code unit} is not supported
 115      */
 116     public long get(TemporalUnit unit);
 117 
 118     /**
 119      * Returns the list of units uniquely defining the value of this TemporalAmount.
 120      * The list of {@code TemporalUnits} is defined by the implementation class.
 121      * The list is a snapshot of the units at the time {@code getUnits}
 122      * is called and is not mutable.
 123      * The units are ordered from longest duration to the shortest duration
 124      * of the unit.
 125      *
 126      * <h3>Specification for implementors</h3>
 127      * The list of units completely and uniquely represents the
 128      * state of the object without omissions, overlaps or duplication.
 129      * The units are in order from longest duration to shortest.
 130      *
 131      * @return the List of {@code TemporalUnits}; not null
 132      */
 133     public List<TemporalUnit> getUnits();
 134 
 135     /**
 136      * Adds to the specified temporal object.
 137      * <p>
 138      * Adds the amount to the specified temporal object using the logic
 139      * encapsulated in the implementing class.
 140      * <p>
 141      * There are two equivalent ways of using this method.
 142      * The first is to invoke this method directly.
 143      * The second is to use {@link Temporal#plus(TemporalAmount)}:
 144      * <pre>
 145      *   // These two lines are equivalent, but the second approach is recommended
 146      *   dateTime = amount.addTo(dateTime);
 147      *   dateTime = dateTime.plus(adder);
 148      * </pre>
 149      * It is recommended to use the second approach, {@code plus(TemporalAmount)},
 150      * as it is a lot clearer to read in code.
 151      *
 152      * <h3>Specification for implementors</h3>
 153      * The implementation must take the input object and add to it.
 154      * The implementation defines the logic of the addition and is responsible for
 155      * documenting that logic. It may use any method on {@code Temporal} to
 156      * query the temporal object and perform the addition.
 157      * The returned object must have the same observable type as the input object
 158      * <p>
 159      * The input object must not be altered.
 160      * Instead, an adjusted copy of the original must be returned.
 161      * This provides equivalent, safe behavior for immutable and mutable temporal objects.
 162      * <p>
 163      * The input temporal object may be in a calendar system other than ISO.
 164      * Implementations may choose to document compatibility with other calendar systems,
 165      * or reject non-ISO temporal objects by {@link Queries#chronology() querying the chronology}.
 166      * <p>
 167      * This method may be called from multiple threads in parallel.
 168      * It must be thread-safe when invoked.
 169      *
 170      * @param temporal  the temporal object to add the amount to, not null
 171      * @return an object of the same observable type with the addition made, not null
 172      * @throws DateTimeException if unable to add
 173      * @throws ArithmeticException if numeric overflow occurs
 174      */
 175     public Temporal addTo(Temporal temporal);
 176 
 177     /**
 178      * Subtracts this object from the specified temporal object.
 179      * <p>
 180      * Subtracts the amount from the specified temporal object using the logic
 181      * encapsulated in the implementing class.
 182      * <p>
 183      * There are two equivalent ways of using this method.
 184      * The first is to invoke this method directly.
 185      * The second is to use {@link Temporal#minus(TemporalAmount)}:
 186      * <pre>
 187      *   // these two lines are equivalent, but the second approach is recommended
 188      *   dateTime = amount.subtractFrom(dateTime);
 189      *   dateTime = dateTime.minus(amount);
 190      * </pre>
 191      * It is recommended to use the second approach, {@code minus(TemporalAmount)},
 192      * as it is a lot clearer to read in code.
 193      *
 194      * <h3>Specification for implementors</h3>
 195      * The implementation must take the input object and subtract from it.
 196      * The implementation defines the logic of the subtraction and is responsible for
 197      * documenting that logic. It may use any method on {@code Temporal} to
 198      * query the temporal object and perform the subtraction.
 199      * The returned object must have the same observable type as the input object
 200      * <p>
 201      * The input object must not be altered.
 202      * Instead, an adjusted copy of the original must be returned.
 203      * This provides equivalent, safe behavior for immutable and mutable temporal objects.
 204      * <p>
 205      * The input temporal object may be in a calendar system other than ISO.
 206      * Implementations may choose to document compatibility with other calendar systems,
 207      * or reject non-ISO temporal objects by {@link Queries#chronology() querying the chronology}.
 208      * <p>
 209      * This method may be called from multiple threads in parallel.
 210      * It must be thread-safe when invoked.
 211      *
 212      * @param temporal  the temporal object to subtract the amount from, not null
 213      * @return an object of the same observable type with the subtraction made, not null
 214      * @throws DateTimeException if unable to subtract
 215      * @throws ArithmeticException if numeric overflow occurs
 216      */
 217     public Temporal subtractFrom(Temporal temporal);
 218 }