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, 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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  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 package java.time.temporal;
  63 
  64 import java.time.DateTimeException;
  65 
  66 /**
  67  * Strategy for querying a temporal object.
  68  * <p>
  69  * Queries are a key tool for extracting information from temporal objects.
  70  * They exist to externalize the process of querying, permitting different
  71  * approaches, as per the strategy design pattern.
  72  * Examples might be a query that checks if the date is the day before February 29th
  73  * in a leap year, or calculates the number of days to your next birthday.
  74  * <p>
  75  * The {@link TemporalField} interface provides another mechanism for querying
  76  * temporal objects. That interface is limited to returning a {@code long}.
  77  * By contrast, queries can return any type.
  78  * <p>
  79  * There are two equivalent ways of using a {@code TemporalQuery}.
  80  * The first is to invoke the method on this interface directly.
  81  * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
  82  * <pre>
  83  *   // these two lines are equivalent, but the second approach is recommended
  84  *   temporal = thisQuery.queryFrom(temporal);
  85  *   temporal = temporal.query(thisQuery);
  86  * </pre>
  87  * It is recommended to use the second approach, {@code query(TemporalQuery)},
  88  * as it is a lot clearer to read in code.
  89  * <p>
  90  * The most common implementations are method references, such as
  91  * {@code LocalDate::from} and {@code ZoneId::from}.
  92  * Further implementations are on {@link Queries}.
  93  * Queries may also be defined by applications.
  94  *
  95  * <h3>Specification for implementors</h3>
  96  * This interface places no restrictions on the mutability of implementations,
  97  * however immutability is strongly recommended.
  98  *
  99  * @since 1.8
 100  */
 101 @FunctionalInterface
 102 public interface TemporalQuery<R> {
 103 
 104     /**
 105      * Queries the specified temporal object.
 106      * <p>
 107      * This queries the specified temporal object to return an object using the logic
 108      * encapsulated in the implementing class.
 109      * Examples might be a query that checks if the date is the day before February 29th
 110      * in a leap year, or calculates the number of days to your next birthday.
 111      * <p>
 112      * There are two equivalent ways of using this method.
 113      * The first is to invoke this method directly.
 114      * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
 115      * <pre>
 116      *   // these two lines are equivalent, but the second approach is recommended
 117      *   temporal = thisQuery.queryFrom(temporal);
 118      *   temporal = temporal.query(thisQuery);
 119      * </pre>
 120      * It is recommended to use the second approach, {@code query(TemporalQuery)},
 121      * as it is a lot clearer to read in code.
 122      *
 123      * <h3>Specification for implementors</h3>
 124      * The implementation must take the input object and query it.
 125      * The implementation defines the logic of the query and is responsible for
 126      * documenting that logic.
 127      * It may use any method on {@code TemporalAccessor} to determine the result.
 128      * The input object must not be altered.
 129      * <p>
 130      * The input temporal object may be in a calendar system other than ISO.
 131      * Implementations may choose to document compatibility with other calendar systems,
 132      * or reject non-ISO temporal objects by {@link Queries#chronology() querying the chronology}.
 133      * <p>
 134      * This method may be called from multiple threads in parallel.
 135      * It must be thread-safe when invoked.
 136      *
 137      * @param temporal  the temporal object to query, not null
 138      * @return the queried value, may return null to indicate not found
 139      * @throws DateTimeException if unable to query
 140      * @throws ArithmeticException if numeric overflow occurs
 141      */
 142     R queryFrom(TemporalAccessor temporal);
 143 
 144 }