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 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 public interface TemporalQuery<R> {
102
103 /**
104 * Queries the specified temporal object.
105 * <p>
106 * This queries the specified temporal object to return an object using the logic
107 * encapsulated in the implementing class.
108 * Examples might be a query that checks if the date is the day before February 29th
109 * in a leap year, or calculates the number of days to your next birthday.
110 * <p>
111 * There are two equivalent ways of using this method.
112 * The first is to invoke this method directly.
113 * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
114 * <pre>
115 * // these two lines are equivalent, but the second approach is recommended
116 * temporal = thisQuery.queryFrom(temporal);
117 * temporal = temporal.query(thisQuery);
118 * </pre>
119 * It is recommended to use the second approach, {@code query(TemporalQuery)},
120 * as it is a lot clearer to read in code.
121 *
122 * <h3>Specification for implementors</h3>
123 * The implementation must take the input object and query it.
124 * The implementation defines the logic of the query and is responsible for
125 * documenting that logic.
126 * It may use any method on {@code TemporalAccessor} to determine the result.
127 * The input object must not be altered.
128 * <p>
129 * The input temporal object may be in a calendar system other than ISO.
130 * Implementations may choose to document compatibility with other calendar systems,
131 * or reject non-ISO temporal objects by {@link Queries#chrono() querying the chronology}.
132 * <p>
133 * This method may be called from multiple threads in parallel.
134 * It must be thread-safe when invoked.
135 *
136 * @param temporal the temporal object to query, not null
137 * @return the queried value, may return null to indicate not found
138 * @throws DateTimeException if unable to query
139 * @throws ArithmeticException if numeric overflow occurs
140 */
141 R queryFrom(TemporalAccessor temporal);
142
143 }