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
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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 import java.time.format.DateTimeBuilder;
66 import java.util.Comparator;
67
68 /**
69 * A field of date-time, such as month-of-year or hour-of-minute.
70 * <p>
71 * Date and time is expressed using fields which partition the time-line into something
72 * meaningful for humans. Implementations of this interface represent those fields.
73 * <p>
74 * The most commonly used units are defined in {@link ChronoField}.
75 * Further fields are supplied in {@link ISOFields}, {@link WeekFields} and {@link JulianFields}.
76 * Fields can also be written by application code by implementing this interface.
77 * <p>
78 * The field works using double dispatch. Client code calls methods on a date-time like
79 * {@code LocalDateTime} which check if the field is a {@code ChronoField}.
80 * If it is, then the date-time must handle it.
81 * Otherwise, the method call is re-dispatched to the matching method in this interface.
82 *
83 * <h3>Specification for implementors</h3>
84 * This interface must be implemented with care to ensure other classes operate correctly.
85 * All implementations that can be instantiated must be final, immutable and thread-safe.
86 * It is recommended to use an enum where possible.
87 *
88 * @since 1.8
89 */
90 public interface TemporalField extends Comparator<TemporalAccessor> {
91
92 /**
93 * Gets a descriptive name for the field.
94 * <p>
95 * The should be of the format 'BaseOfRange', such as 'MonthOfYear',
96 * unless the field has a range of {@code FOREVER}, when only
97 * the base unit is mentioned, such as 'Year' or 'Era'.
98 *
99 * @return the name, not null
100 */
101 String getName();
102
103 /**
104 * Gets the unit that the field is measured in.
105 * <p>
106 * The unit of the field is the period that varies within the range.
107 * For example, in the field 'MonthOfYear', the unit is 'Months'.
108 * See also {@link #getRangeUnit()}.
109 *
110 * @return the period unit defining the base unit of the field, not null
111 */
112 TemporalUnit getBaseUnit();
113
114 /**
115 * Gets the range that the field is bound by.
116 * <p>
117 * The range of the field is the period that the field varies within.
118 * For example, in the field 'MonthOfYear', the range is 'Years'.
119 * See also {@link #getBaseUnit()}.
120 * <p>
121 * The range is never null. For example, the 'Year' field is shorthand for
122 * 'YearOfForever'. It therefore has a unit of 'Years' and a range of 'Forever'.
123 *
124 * @return the period unit defining the range of the field, not null
125 */
126 TemporalUnit getRangeUnit();
127
128 //-----------------------------------------------------------------------
129 /**
130 * Compares the value of this field in two temporal objects.
131 * <p>
132 * All fields implement {@link Comparator} on {@link TemporalAccessor}.
133 * This allows a list of date-times to be compared using the value of a field.
134 * For example, you could sort a list of arbitrary temporal objects by the value of
135 * the month-of-year field - {@code Collections.sort(list, MONTH_OF_YEAR)}
136 * <p>
137 * The default implementation must behave equivalent to this code:
138 * <pre>
139 * return Long.compare(temporal1.getLong(this), temporal2.getLong(this));
140 * </pre>
141 *
142 * @param temporal1 the first temporal object to compare, not null
143 * @param temporal2 the second temporal object to compare, not null
144 * @throws DateTimeException if unable to obtain the value for this field
145 */
146 public default int compare(TemporalAccessor temporal1, TemporalAccessor temporal2) {
147 return Long.compare(temporal1.getLong(this), temporal2.getLong(this));
148 }
149
150 /**
151 * Gets the range of valid values for the field.
152 * <p>
153 * All fields can be expressed as a {@code long} integer.
154 * This method returns an object that describes the valid range for that value.
155 * This method is generally only applicable to the ISO-8601 calendar system.
156 * <p>
157 * Note that the result only describes the minimum and maximum valid values
158 * and it is important not to read too much into them. For example, there
159 * could be values within the range that are invalid for the field.
160 *
161 * @return the range of valid values for the field, not null
162 */
163 ValueRange range();
164
165 //-----------------------------------------------------------------------
166 /**
167 * Checks if this field is supported by the temporal object.
168 * <p>
169 * This determines whether the temporal accessor supports this field.
170 * If this returns false, the the temporal cannot be queried for this field.
171 * <p>
172 * There are two equivalent ways of using this method.
173 * The first is to invoke this method directly.
174 * The second is to use {@link TemporalAccessor#isSupported(TemporalField)}:
175 * <pre>
176 * // these two lines are equivalent, but the second approach is recommended
177 * temporal = thisField.doIsSupported(temporal);
178 * temporal = temporal.isSupported(thisField);
179 * </pre>
180 * It is recommended to use the second approach, {@code isSupported(TemporalField)},
181 * as it is a lot clearer to read in code.
182 * <p>
183 * Implementations should determine whether they are supported using the fields
184 * available in {@link ChronoField}.
185 *
186 * @param temporal the temporal object to query, not null
187 * @return true if the date-time can be queried for this field, false if not
188 */
189 boolean doIsSupported(TemporalAccessor temporal);
190
191 /**
192 * Get the range of valid values for this field using the temporal object to
193 * refine the result.
194 * <p>
195 * This uses the temporal object to find the range of valid values for the field.
196 * This is similar to {@link #range()}, however this method refines the result
197 * using the temporal. For example, if the field is {@code DAY_OF_MONTH} the
198 * {@code range} method is not accurate as there are four possible month lengths,
199 * 28, 29, 30 and 31 days. Using this method with a date allows the range to be
200 * accurate, returning just one of those four options.
201 * <p>
202 * There are two equivalent ways of using this method.
203 * The first is to invoke this method directly.
204 * The second is to use {@link TemporalAccessor#range(TemporalField)}:
205 * <pre>
206 * // these two lines are equivalent, but the second approach is recommended
207 * temporal = thisField.doRange(temporal);
208 * temporal = temporal.range(thisField);
209 * </pre>
210 * It is recommended to use the second approach, {@code range(TemporalField)},
211 * as it is a lot clearer to read in code.
212 * <p>
213 * Implementations should perform any queries or calculations using the fields
214 * available in {@link ChronoField}.
215 * If the field is not supported a {@code DateTimeException} must be thrown.
216 *
217 * @param temporal the temporal object used to refine the result, not null
218 * @return the range of valid values for this field, not null
219 * @throws DateTimeException if the range for the field cannot be obtained
220 */
221 ValueRange doRange(TemporalAccessor temporal);
222
223 /**
224 * Gets the value of this field from the specified temporal object.
225 * <p>
226 * This queries the temporal object for the value of this field.
227 * <p>
228 * There are two equivalent ways of using this method.
229 * The first is to invoke this method directly.
230 * The second is to use {@link TemporalAccessor#getLong(TemporalField)}
231 * (or {@link TemporalAccessor#get(TemporalField)}):
232 * <pre>
233 * // these two lines are equivalent, but the second approach is recommended
234 * temporal = thisField.doGet(temporal);
235 * temporal = temporal.getLong(thisField);
236 * </pre>
237 * It is recommended to use the second approach, {@code getLong(TemporalField)},
238 * as it is a lot clearer to read in code.
239 * <p>
240 * Implementations should perform any queries or calculations using the fields
241 * available in {@link ChronoField}.
242 * If the field is not supported a {@code DateTimeException} must be thrown.
243 *
244 * @param temporal the temporal object to query, not null
245 * @return the value of this field, not null
246 * @throws DateTimeException if a value for the field cannot be obtained
247 */
248 long doGet(TemporalAccessor temporal);
249
250 /**
251 * Returns a copy of the specified temporal object with the value of this field set.
252 * <p>
253 * This returns a new temporal object based on the specified one with the value for
254 * this field changed. For example, on a {@code LocalDate}, this could be used to
255 * set the year, month or day-of-month.
256 * The returned object has the same observable type as the specified object.
257 * <p>
258 * In some cases, changing a field is not fully defined. For example, if the target object is
259 * a date representing the 31st January, then changing the month to February would be unclear.
260 * In cases like this, the implementation is responsible for resolving the result.
261 * Typically it will choose the previous valid date, which would be the last valid
262 * day of February in this example.
263 * <p>
264 * There are two equivalent ways of using this method.
265 * The first is to invoke this method directly.
266 * The second is to use {@link Temporal#with(TemporalField, long)}:
267 * <pre>
268 * // these two lines are equivalent, but the second approach is recommended
269 * temporal = thisField.doWith(temporal);
270 * temporal = temporal.with(thisField);
271 * </pre>
272 * It is recommended to use the second approach, {@code with(TemporalField)},
273 * as it is a lot clearer to read in code.
274 * <p>
275 * Implementations should perform any queries or calculations using the fields
276 * available in {@link ChronoField}.
277 * If the field is not supported a {@code DateTimeException} must be thrown.
278 * <p>
279 * Implementations must not alter the specified temporal object.
280 * Instead, an adjusted copy of the original must be returned.
281 * This provides equivalent, safe behavior for immutable and mutable implementations.
282 *
283 * @param <R> the type of the Temporal object
284 * @param temporal the temporal object to adjust, not null
285 * @param newValue the new value of the field
286 * @return the adjusted temporal object, not null
287 * @throws DateTimeException if the field cannot be set
288 */
289 <R extends Temporal> R doWith(R temporal, long newValue);
290
291 /**
292 * Resolves the date/time information in the builder
293 * <p>
294 * This method is invoked during the resolve of the builder.
295 * Implementations should combine the associated field with others to form
296 * objects like {@code LocalDate}, {@code LocalTime} and {@code LocalDateTime}
297 *
298 * @param builder the builder to resolve, not null
299 * @param value the value of the associated field
300 * @return true if builder has been changed, false otherwise
301 * @throws DateTimeException if unable to resolve
302 */
303 boolean resolve(DateTimeBuilder builder, long value);
304
305 }