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
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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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
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.chrono;
63
64 import static java.time.temporal.ChronoField.ERA;
65 import static java.time.temporal.ChronoUnit.ERAS;
66
67 import java.time.DateTimeException;
68 import java.time.format.DateTimeFormatterBuilder;
69 import java.time.format.TextStyle;
70 import java.time.temporal.ChronoField;
71 import java.time.temporal.Queries;
72 import java.time.temporal.Temporal;
73 import java.time.temporal.TemporalAccessor;
74 import java.time.temporal.TemporalAdjuster;
75 import java.time.temporal.TemporalField;
76 import java.time.temporal.TemporalQuery;
77 import java.time.temporal.ValueRange;
78 import java.util.Locale;
79
80 /**
81 * An era of the time-line.
82 * <p>
83 * Most calendar systems have a single epoch dividing the time-line into two eras.
84 * However, some calendar systems, have multiple eras, such as one for the reign
85 * of each leader.
86 * In all cases, the era is conceptually the largest division of the time-line.
87 * Each chronology defines the Era's that are known Eras and a
88 * {@link Chronology#eras Chronology.eras} to get the valid eras.
89 * <p>
90 * For example, the Thai Buddhist calendar system divides time into two eras,
91 * before and after a single date. By contrast, the Japanese calendar system
92 * has one era for the reign of each Emperor.
93 * <p>
94 * Instances of {@code Era} may be compared using the {@code ==} operator.
95 *
96 * <h3>Specification for implementors</h3>
97 * This interface must be implemented with care to ensure other classes operate correctly.
98 * All implementations must be singletons - final, immutable and thread-safe.
99 * It is recommended to use an enum whenever possible.
100 *
101 * @since 1.8
102 */
103 public interface Era extends TemporalAccessor, TemporalAdjuster {
104
105 /**
106 * Gets the numeric value associated with the era as defined by the chronology.
107 * Each chronology defines the predefined Eras and methods to list the Eras
108 * of the chronology.
109 * <p>
110 * All fields, including eras, have an associated numeric value.
111 * The meaning of the numeric value for era is determined by the chronology
112 * according to these principles:
113 * <p><ul>
114 * <li>The era in use at the epoch 1970-01-01 (ISO) has the value 1.
115 * <li>Later eras have sequentially higher values.
116 * <li>Earlier eras have sequentially lower values, which may be negative.
117 * </ul><p>
118 *
119 * @return the numeric era value
120 */
121 int getValue();
122
123 /**
124 * Gets the chronology of this era.
125 * <p>
126 * The {@code Chronology} represents the calendar system in use.
127 * This always returns the standard form of the chronology.
128 *
129 * @return the chronology, not null
130 */
131 Chronology getChronology();
132
133 //-----------------------------------------------------------------------
134 /**
135 * Obtains a date in this era given the year-of-era, month, and day.
136 * <p>
137 * This era is combined with the given date fields to form a date.
138 * The year specified must be the year-of-era.
139 * Methods to create a date from the proleptic-year are on {@code Chronology}.
140 * This always uses the standard form of the chronology.
141 * <p>
142 * This default implementation invokes the factory method on {@link Chronology}.
143 *
144 * @param yearOfEra the calendar system year-of-era
145 * @param month the calendar system month-of-year
146 * @param day the calendar system day-of-month
147 * @return a local date based on this era and the specified year-of-era, month and day
148 */
149 public default ChronoLocalDate date(int yearOfEra, int month, int day) {
150 return getChronology().date(this, yearOfEra, month, day);
151 }
152
153
154 /**
155 * Obtains a date in this era given year-of-era and day-of-year fields.
156 * <p>
157 * This era is combined with the given date fields to form a date.
158 * The year specified must be the year-of-era.
159 * Methods to create a date from the proleptic-year are on {@code Chronology}.
160 * This always uses the standard form of the chronology.
161 * <p>
162 * This default implementation invokes the factory method on {@link Chronology}.
163 *
164 * @param yearOfEra the calendar system year-of-era
165 * @param dayOfYear the calendar system day-of-year
166 * @return a local date based on this era and the specified year-of-era and day-of-year
167 */
168 public default ChronoLocalDate dateYearDay(int yearOfEra, int dayOfYear) {
169 return getChronology().dateYearDay(this, yearOfEra, dayOfYear);
170 }
171
172 //-----------------------------------------------------------------------
173 /**
174 * Checks if the specified field is supported.
175 * <p>
176 * This checks if this era can be queried for the specified field.
177 * If false, then calling the {@link #range(TemporalField) range} and
178 * {@link #get(TemporalField) get} methods will throw an exception.
179 * <p>
180 * If the field is a {@link ChronoField} then the query is implemented here.
181 * The {@code ERA} field returns true.
182 * All other {@code ChronoField} instances will return false.
183 * <p>
184 * If the field is not a {@code ChronoField}, then the result of this method
185 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
186 * passing {@code this} as the argument.
187 * Whether the field is supported is determined by the field.
188 *
189 * @param field the field to check, null returns false
190 * @return true if the field is supported on this era, false if not
191 */
192 @Override
193 public default boolean isSupported(TemporalField field) {
194 if (field instanceof ChronoField) {
195 return field == ERA;
196 }
197 return field != null && field.isSupportedBy(this);
198 }
199
200 /**
201 * Gets the range of valid values for the specified field.
202 * <p>
203 * The range object expresses the minimum and maximum valid values for a field.
204 * This era is used to enhance the accuracy of the returned range.
205 * If it is not possible to return the range, because the field is not supported
206 * or for some other reason, an exception is thrown.
207 * <p>
208 * If the field is a {@link ChronoField} then the query is implemented here.
209 * The {@code ERA} field returns the range.
210 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
211 * <p>
212 * If the field is not a {@code ChronoField}, then the result of this method
213 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
214 * passing {@code this} as the argument.
215 * Whether the range can be obtained is determined by the field.
216 *
217 * @param field the field to query the range for, not null
218 * @return the range of valid values for the field, not null
219 * @throws DateTimeException if the range for the field cannot be obtained
220 */
221 @Override // override for Javadoc
222 public default ValueRange range(TemporalField field) {
223 return TemporalAccessor.super.range(field);
224 }
225
226 /**
227 * Gets the value of the specified field from this era as an {@code int}.
228 * <p>
229 * This queries this era for the value for the specified field.
230 * The returned value will always be within the valid range of values for the field.
231 * If it is not possible to return the value, because the field is not supported
232 * or for some other reason, an exception is thrown.
233 * <p>
234 * If the field is a {@link ChronoField} then the query is implemented here.
235 * The {@code ERA} field returns the value of the era.
236 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
237 * <p>
238 * If the field is not a {@code ChronoField}, then the result of this method
239 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
240 * passing {@code this} as the argument. Whether the value can be obtained,
241 * and what the value represents, is determined by the field.
242 *
243 * @param field the field to get, not null
244 * @return the value for the field
245 * @throws DateTimeException if a value for the field cannot be obtained
246 * @throws ArithmeticException if numeric overflow occurs
247 */
248 @Override // override for Javadoc and performance
249 public default int get(TemporalField field) {
250 if (field == ERA) {
251 return getValue();
252 }
253 return range(field).checkValidIntValue(getLong(field), field);
254 }
255
256 /**
257 * Gets the value of the specified field from this era as a {@code long}.
258 * <p>
259 * This queries this era for the value for the specified field.
260 * If it is not possible to return the value, because the field is not supported
261 * or for some other reason, an exception is thrown.
262 * <p>
263 * If the field is a {@link ChronoField} then the query is implemented here.
264 * The {@code ERA} field returns the value of the era.
265 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
266 * <p>
267 * If the field is not a {@code ChronoField}, then the result of this method
268 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
269 * passing {@code this} as the argument. Whether the value can be obtained,
270 * and what the value represents, is determined by the field.
271 *
272 * @param field the field to get, not null
273 * @return the value for the field
274 * @throws DateTimeException if a value for the field cannot be obtained
275 * @throws ArithmeticException if numeric overflow occurs
276 */
277 @Override
278 public default long getLong(TemporalField field) {
279 if (field == ERA) {
280 return getValue();
281 } else if (field instanceof ChronoField) {
282 throw new DateTimeException("Unsupported field: " + field.getName());
283 }
284 return field.getFrom(this);
285 }
286
287 //-----------------------------------------------------------------------
288 /**
289 * Queries this era using the specified query.
290 * <p>
291 * This queries this era using the specified query strategy object.
292 * The {@code TemporalQuery} object defines the logic to be used to
293 * obtain the result. Read the documentation of the query to understand
294 * what the result of this method will be.
295 * <p>
296 * The result of this method is obtained by invoking the
297 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
298 * specified query passing {@code this} as the argument.
299 *
300 * @param <R> the type of the result
301 * @param query the query to invoke, not null
302 * @return the query result, null may be returned (defined by the query)
303 * @throws DateTimeException if unable to query (defined by the query)
304 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
305 */
306 @SuppressWarnings("unchecked")
307 @Override
308 public default <R> R query(TemporalQuery<R> query) {
309 if (query == Queries.chronology()) {
310 return (R) getChronology();
311 } else if (query == Queries.precision()) {
312 return (R) ERAS;
313 }
314 return TemporalAccessor.super.query(query);
315 }
316
317 /**
318 * Adjusts the specified temporal object to have the same era as this object.
319 * <p>
320 * This returns a temporal object of the same observable type as the input
321 * with the era changed to be the same as this.
322 * <p>
323 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
324 * passing {@link ChronoField#ERA} as the field.
325 * <p>
326 * In most cases, it is clearer to reverse the calling pattern by using
327 * {@link Temporal#with(TemporalAdjuster)}:
328 * <pre>
329 * // these two lines are equivalent, but the second approach is recommended
330 * temporal = thisEra.adjustInto(temporal);
331 * temporal = temporal.with(thisEra);
332 * </pre>
333 * <p>
334 * This instance is immutable and unaffected by this method call.
335 *
336 * @param temporal the target object to be adjusted, not null
337 * @return the adjusted object, not null
338 * @throws DateTimeException if unable to make the adjustment
339 * @throws ArithmeticException if numeric overflow occurs
340 */
341 @Override
342 public default Temporal adjustInto(Temporal temporal) {
343 return temporal.with(ERA, getValue());
344 }
345
346 //-----------------------------------------------------------------------
347 /**
348 * Gets the textual representation of this era.
349 * <p>
350 * This returns the textual name used to identify the era,
351 * suitable for presentation to the user.
352 * The parameters control the style of the returned text and the locale.
353 * <p>
354 * If no textual mapping is found then the {@link #getValue() numeric value} is returned.
355 * <p>
356 * This default implementation is suitable for all implementations.
357 *
358 * @param style the style of the text required, not null
359 * @param locale the locale to use, not null
360 * @return the text value of the era, not null
361 */
362 public default String getDisplayName(TextStyle style, Locale locale) {
363 return new DateTimeFormatterBuilder().appendText(ERA, style).toFormatter(locale).format(this);
364 }
365
366 // NOTE: methods to convert year-of-era/proleptic-year cannot be here as they may depend on month/day (Japanese)
367 }