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
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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.ZoneId;
66 import java.time.chrono.ChronoLocalDate;
67 import java.time.chrono.Chronology;
68 import java.time.format.ResolverStyle;
69 import java.util.Locale;
70 import java.util.Map;
71 import java.util.Objects;
72
73 /**
74 * A field of date-time, such as month-of-year or hour-of-minute.
75 * <p>
76 * Date and time is expressed using fields which partition the time-line into something
77 * meaningful for humans. Implementations of this interface represent those fields.
78 * <p>
79 * The most commonly used units are defined in {@link ChronoField}.
80 * Further fields are supplied in {@link IsoFields}, {@link WeekFields} and {@link JulianFields}.
81 * Fields can also be written by application code by implementing this interface.
82 * <p>
83 * The field works using double dispatch. Client code calls methods on a date-time like
84 * {@code LocalDateTime} which check if the field is a {@code ChronoField}.
85 * If it is, then the date-time must handle it.
86 * Otherwise, the method call is re-dispatched to the matching method in this interface.
87 *
88 * @implSpec
89 * This interface must be implemented with care to ensure other classes operate correctly.
90 * All implementations that can be instantiated must be final, immutable and thread-safe.
91 * Implementations should be {@code Serializable} where possible.
92 * An enum is as effective implementation choice.
93 *
94 * @since 1.8
95 */
96 public interface TemporalField {
97
98 /**
99 * Gets the display name for the field in the requested locale.
100 * <p>
101 * If there is no display name for the locale then a suitable default must be returned.
102 * <p>
103 * The default implementation must check the locale is not null
104 * and return {@code toString()}.
105 *
106 * @param locale the locale to use, not null
107 * @return the display name for the locale or a suitable default, not null
108 */
109 default String getDisplayName(Locale locale) {
110 Objects.requireNonNull(locale, "locale");
111 return toString();
112 }
113
114 /**
115 * Gets the unit that the field is measured in.
116 * <p>
117 * The unit of the field is the period that varies within the range.
118 * For example, in the field 'MonthOfYear', the unit is 'Months'.
119 * See also {@link #getRangeUnit()}.
120 *
121 * @return the period unit defining the base unit of the field, not null
122 */
123 TemporalUnit getBaseUnit();
124
125 /**
126 * Gets the range that the field is bound by.
127 * <p>
128 * The range of the field is the period that the field varies within.
129 * For example, in the field 'MonthOfYear', the range is 'Years'.
130 * See also {@link #getBaseUnit()}.
131 * <p>
132 * The range is never null. For example, the 'Year' field is shorthand for
133 * 'YearOfForever'. It therefore has a unit of 'Years' and a range of 'Forever'.
134 *
135 * @return the period unit defining the range of the field, not null
136 */
137 TemporalUnit getRangeUnit();
138
139 /**
140 * Gets the range of valid values for the field.
141 * <p>
142 * All fields can be expressed as a {@code long} integer.
143 * This method returns an object that describes the valid range for that value.
144 * This method is generally only applicable to the ISO-8601 calendar system.
145 * <p>
146 * Note that the result only describes the minimum and maximum valid values
147 * and it is important not to read too much into them. For example, there
148 * could be values within the range that are invalid for the field.
149 *
150 * @return the range of valid values for the field, not null
151 */
152 ValueRange range();
153
154 //-----------------------------------------------------------------------
155 /**
156 * Checks if this field represents a component of a date.
157 * <p>
158 * A field is date-based if it can be derived from
159 * {@link ChronoField#EPOCH_DAY EPOCH_DAY}.
160 * Note that it is valid for both {@code isDateBased()} and {@code isTimeBased()}
161 * to return false, such as when representing a field like minute-of-week.
162 *
163 * @return true if this field is a component of a date
164 */
165 boolean isDateBased();
166
167 /**
168 * Checks if this field represents a component of a time.
169 * <p>
170 * A field is time-based if it can be derived from
171 * {@link ChronoField#NANO_OF_DAY NANO_OF_DAY}.
172 * Note that it is valid for both {@code isDateBased()} and {@code isTimeBased()}
173 * to return false, such as when representing a field like minute-of-week.
174 *
175 * @return true if this field is a component of a time
176 */
177 boolean isTimeBased();
178
179 //-----------------------------------------------------------------------
180 /**
181 * Checks if this field is supported by the temporal object.
182 * <p>
183 * This determines whether the temporal accessor supports this field.
184 * If this returns false, the the temporal cannot be queried for this field.
185 * <p>
186 * There are two equivalent ways of using this method.
187 * The first is to invoke this method directly.
188 * The second is to use {@link TemporalAccessor#isSupported(TemporalField)}:
189 * <pre>
190 * // these two lines are equivalent, but the second approach is recommended
191 * temporal = thisField.isSupportedBy(temporal);
192 * temporal = temporal.isSupported(thisField);
193 * </pre>
194 * It is recommended to use the second approach, {@code isSupported(TemporalField)},
195 * as it is a lot clearer to read in code.
196 * <p>
197 * Implementations should determine whether they are supported using the fields
198 * available in {@link ChronoField}.
199 *
200 * @param temporal the temporal object to query, not null
201 * @return true if the date-time can be queried for this field, false if not
202 */
203 boolean isSupportedBy(TemporalAccessor temporal);
204
205 /**
206 * Get the range of valid values for this field using the temporal object to
207 * refine the result.
208 * <p>
209 * This uses the temporal object to find the range of valid values for the field.
210 * This is similar to {@link #range()}, however this method refines the result
211 * using the temporal. For example, if the field is {@code DAY_OF_MONTH} the
212 * {@code range} method is not accurate as there are four possible month lengths,
213 * 28, 29, 30 and 31 days. Using this method with a date allows the range to be
214 * accurate, returning just one of those four options.
215 * <p>
216 * There are two equivalent ways of using this method.
217 * The first is to invoke this method directly.
218 * The second is to use {@link TemporalAccessor#range(TemporalField)}:
219 * <pre>
220 * // these two lines are equivalent, but the second approach is recommended
221 * temporal = thisField.rangeRefinedBy(temporal);
222 * temporal = temporal.range(thisField);
223 * </pre>
224 * It is recommended to use the second approach, {@code range(TemporalField)},
225 * as it is a lot clearer to read in code.
226 * <p>
227 * Implementations should perform any queries or calculations using the fields
228 * available in {@link ChronoField}.
229 * If the field is not supported an {@code UnsupportedTemporalTypeException} must be thrown.
230 *
231 * @param temporal the temporal object used to refine the result, not null
232 * @return the range of valid values for this field, not null
233 * @throws DateTimeException if the range for the field cannot be obtained
234 * @throws UnsupportedTemporalTypeException if the field is not supported by the temporal
235 */
236 ValueRange rangeRefinedBy(TemporalAccessor temporal);
237
238 /**
239 * Gets the value of this field from the specified temporal object.
240 * <p>
241 * This queries the temporal object for the value of this field.
242 * <p>
243 * There are two equivalent ways of using this method.
244 * The first is to invoke this method directly.
245 * The second is to use {@link TemporalAccessor#getLong(TemporalField)}
246 * (or {@link TemporalAccessor#get(TemporalField)}):
247 * <pre>
248 * // these two lines are equivalent, but the second approach is recommended
249 * temporal = thisField.getFrom(temporal);
250 * temporal = temporal.getLong(thisField);
251 * </pre>
252 * It is recommended to use the second approach, {@code getLong(TemporalField)},
253 * as it is a lot clearer to read in code.
254 * <p>
255 * Implementations should perform any queries or calculations using the fields
256 * available in {@link ChronoField}.
257 * If the field is not supported an {@code UnsupportedTemporalTypeException} must be thrown.
258 *
259 * @param temporal the temporal object to query, not null
260 * @return the value of this field, not null
261 * @throws DateTimeException if a value for the field cannot be obtained
262 * @throws UnsupportedTemporalTypeException if the field is not supported by the temporal
263 * @throws ArithmeticException if numeric overflow occurs
264 */
265 long getFrom(TemporalAccessor temporal);
266
267 /**
268 * Returns a copy of the specified temporal object with the value of this field set.
269 * <p>
270 * This returns a new temporal object based on the specified one with the value for
271 * this field changed. For example, on a {@code LocalDate}, this could be used to
272 * set the year, month or day-of-month.
273 * The returned object has the same observable type as the specified object.
274 * <p>
275 * In some cases, changing a field is not fully defined. For example, if the target object is
276 * a date representing the 31st January, then changing the month to February would be unclear.
277 * In cases like this, the implementation is responsible for resolving the result.
278 * Typically it will choose the previous valid date, which would be the last valid
279 * day of February in this example.
280 * <p>
281 * There are two equivalent ways of using this method.
282 * The first is to invoke this method directly.
283 * The second is to use {@link Temporal#with(TemporalField, long)}:
284 * <pre>
285 * // these two lines are equivalent, but the second approach is recommended
286 * temporal = thisField.adjustInto(temporal);
287 * temporal = temporal.with(thisField);
288 * </pre>
289 * It is recommended to use the second approach, {@code with(TemporalField)},
290 * as it is a lot clearer to read in code.
291 * <p>
292 * Implementations should perform any queries or calculations using the fields
293 * available in {@link ChronoField}.
294 * If the field is not supported an {@code UnsupportedTemporalTypeException} must be thrown.
295 * <p>
296 * Implementations must not alter the specified temporal object.
297 * Instead, an adjusted copy of the original must be returned.
298 * This provides equivalent, safe behavior for immutable and mutable implementations.
299 *
300 * @param <R> the type of the Temporal object
301 * @param temporal the temporal object to adjust, not null
302 * @param newValue the new value of the field
303 * @return the adjusted temporal object, not null
304 * @throws DateTimeException if the field cannot be set
305 * @throws UnsupportedTemporalTypeException if the field is not supported by the temporal
306 * @throws ArithmeticException if numeric overflow occurs
307 */
308 <R extends Temporal> R adjustInto(R temporal, long newValue);
309
310 /**
311 * Resolves this field to provide a simpler alternative or a date.
312 * <p>
313 * This method is invoked during the resolve phase of parsing.
314 * It is designed to allow application defined fields to be simplified into
315 * more standard fields, such as those on {@code ChronoField}, or into a date.
316 * <p>
317 * Applications should not normally invoke this method directly.
318 *
319 * @implSpec
320 * If an implementation represents a field that can be simplified, or
321 * combined with others, then this method must be implemented.
322 * <p>
323 * The specified map contains the current state of the parse.
324 * The map is mutable and must be mutated to resolve the field and
325 * any related fields. This method will only be invoked during parsing
326 * if the map contains this field, and implementations should therefore
327 * assume this field is present.
328 * <p>
329 * Resolving a field will consist of looking at the value of this field,
330 * and potentially other fields, and either updating the map with a
331 * simpler value, such as a {@code ChronoField}, or returning a
332 * complete {@code ChronoLocalDate}. If a resolve is successful,
333 * the code must remove all the fields that were resolved from the map,
334 * including this field.
335 * <p>
336 * For example, the {@code IsoFields} class contains the quarter-of-year
337 * and day-of-quarter fields. The implementation of this method in that class
338 * resolves the two fields plus the {@link ChronoField#YEAR YEAR} into a
339 * complete {@code LocalDate}. The resolve method will remove all three
340 * fields from the map before returning the {@code LocalDate}.
341 * <p>
342 * If resolution should be possible, but the data is invalid, the resolver
343 * style should be used to determine an appropriate level of leniency, which
344 * may require throwing a {@code DateTimeException} or {@code ArithmeticException}.
345 * If no resolution is possible, the resolve method must return null.
346 * <p>
347 * When resolving time fields, the map will be altered and null returned.
348 * When resolving date fields, the date is normally returned from the method,
349 * with the map altered to remove the resolved fields. However, it would also
350 * be acceptable for the date fields to be resolved into other {@code ChronoField}
351 * instances that can produce a date, such as {@code EPOCH_DAY}.
352 * <p>
353 * The zone is not normally required for resolution, but is provided for completeness.
354 * <p>
355 * The default implementation must return null.
356 *
357 * @param fieldValues the map of fields to values, which can be updated, not null
358 * @param chronology the effective chronology, not null
359 * @param zone the effective zone, not null
360 * @param resolverStyle the requested type of resolve, not null
361 * @return the resolved date; null if resolving only changed the map,
362 * or no resolve occurred
363 * @throws ArithmeticException if numeric overflow occurs
364 * @throws DateTimeException if resolving results in an error. This must not be thrown
365 * by querying a field on the temporal without first checking if it is supported
366 */
367 default ChronoLocalDate resolve(
368 Map<TemporalField, Long> fieldValues, Chronology chronology,
369 ZoneId zone, ResolverStyle resolverStyle) {
370 return null;
371 }
372
373 /**
374 * Gets a descriptive name for the field.
375 * <p>
376 * The should be of the format 'BaseOfRange', such as 'MonthOfYear',
377 * unless the field has a range of {@code FOREVER}, when only
378 * the base unit is mentioned, such as 'Year' or 'Era'.
379 *
380 * @return the name of the field, not null
381 */
382 @Override
383 String toString();
384
385
386 }