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