1 /* 2 * Copyright (c) 2012, 2015, 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.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.temporal.UnsupportedTemporalTypeException; 69 import java.time.format.DateTimeFormatterBuilder; 70 import java.time.format.TextStyle; 71 import java.time.temporal.ChronoField; 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.TemporalQueries; 77 import java.time.temporal.TemporalQuery; 78 import java.time.temporal.ValueRange; 79 import java.util.Locale; 80 81 /** 82 * An era of the time-line. 83 * <p> 84 * Most calendar systems have a single epoch dividing the time-line into two eras. 85 * However, some calendar systems, have multiple eras, such as one for the reign 86 * of each leader. 87 * In all cases, the era is conceptually the largest division of the time-line. 88 * Each chronology defines the Era's that are known Eras and a 89 * {@link Chronology#eras Chronology.eras} to get the valid eras. 90 * <p> 91 * For example, the Thai Buddhist calendar system divides time into two eras, 92 * before and after a single date. By contrast, the Japanese calendar system 93 * has one era for the reign of each Emperor. 94 * <p> 95 * Instances of {@code Era} may be compared using the {@code ==} operator. 96 * 97 * @implSpec 98 * This interface must be implemented with care to ensure other classes operate correctly. 99 * All implementations must be singletons - final, immutable and thread-safe. 100 * It is recommended to use an enum whenever possible. 101 * 102 * @since 1.8 103 */ 104 public interface Era extends TemporalAccessor, TemporalAdjuster { 105 106 /** 107 * Gets the numeric value associated with the era as defined by the chronology. 108 * Each chronology defines the predefined Eras and methods to list the Eras 109 * of the chronology. 110 * <p> 111 * All fields, including eras, have an associated numeric value. 112 * The meaning of the numeric value for era is determined by the chronology 113 * according to these principles: 114 * <ul> 115 * <li>The era in use at the epoch 1970-01-01 (ISO) has the value 1. 116 * <li>Later eras have sequentially higher values. 117 * <li>Earlier eras have sequentially lower values, which may be negative. 118 * </ul> 119 * 120 * @return the numeric era value 121 */ 122 int getValue(); 123 124 //----------------------------------------------------------------------- 125 /** 126 * Checks if the specified field is supported. 127 * <p> 128 * This checks if this era can be queried for the specified field. 129 * If false, then calling the {@link #range(TemporalField) range} and 130 * {@link #get(TemporalField) get} methods will throw an exception. 131 * <p> 132 * If the field is a {@link ChronoField} then the query is implemented here. 133 * The {@code ERA} field returns true. 134 * All other {@code ChronoField} instances will return false. 135 * <p> 136 * If the field is not a {@code ChronoField}, then the result of this method 137 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)} 138 * passing {@code this} as the argument. 139 * Whether the field is supported is determined by the field. 140 * 141 * @param field the field to check, null returns false 142 * @return true if the field is supported on this era, false if not 143 */ 144 @Override 145 default boolean isSupported(TemporalField field) { 146 if (field instanceof ChronoField) { 147 return field == ERA; 148 } 149 return field != null && field.isSupportedBy(this); 150 } 151 152 /** 153 * Gets the range of valid values for the specified field. 154 * <p> 155 * The range object expresses the minimum and maximum valid values for a field. 156 * This era is used to enhance the accuracy of the returned range. 157 * If it is not possible to return the range, because the field is not supported 158 * or for some other reason, an exception is thrown. 159 * <p> 160 * If the field is a {@link ChronoField} then the query is implemented here. 161 * The {@code ERA} field returns the range. 162 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 163 * <p> 164 * If the field is not a {@code ChronoField}, then the result of this method 165 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)} 166 * passing {@code this} as the argument. 167 * Whether the range can be obtained is determined by the field. 168 * <p> 169 * The default implementation must return a range for {@code ERA} from 170 * zero to one, suitable for two era calendar systems such as ISO. 171 * 172 * @param field the field to query the range for, not null 173 * @return the range of valid values for the field, not null 174 * @throws DateTimeException if the range for the field cannot be obtained 175 * @throws UnsupportedTemporalTypeException if the unit is not supported 176 */ 177 @Override // override for Javadoc 178 default ValueRange range(TemporalField field) { 179 return TemporalAccessor.super.range(field); 180 } 181 182 /** 183 * Gets the value of the specified field from this era as an {@code int}. 184 * <p> 185 * This queries this era for the value of the specified field. 186 * The returned value will always be within the valid range of values for the field. 187 * If it is not possible to return the value, because the field is not supported 188 * or for some other reason, an exception is thrown. 189 * <p> 190 * If the field is a {@link ChronoField} then the query is implemented here. 191 * The {@code ERA} field returns the value of the era. 192 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 193 * <p> 194 * If the field is not a {@code ChronoField}, then the result of this method 195 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} 196 * passing {@code this} as the argument. Whether the value can be obtained, 197 * and what the value represents, is determined by the field. 198 * 199 * @param field the field to get, not null 200 * @return the value for the field 201 * @throws DateTimeException if a value for the field cannot be obtained or 202 * the value is outside the range of valid values for the field 203 * @throws UnsupportedTemporalTypeException if the field is not supported or 204 * the range of values exceeds an {@code int} 205 * @throws ArithmeticException if numeric overflow occurs 206 */ 207 @Override // override for Javadoc and performance 208 default int get(TemporalField field) { 209 if (field == ERA) { 210 return getValue(); 211 } 212 return TemporalAccessor.super.get(field); 213 } 214 215 /** 216 * Gets the value of the specified field from this era as a {@code long}. 217 * <p> 218 * This queries this era for the value of the specified field. 219 * If it is not possible to return the value, because the field is not supported 220 * or for some other reason, an exception is thrown. 221 * <p> 222 * If the field is a {@link ChronoField} then the query is implemented here. 223 * The {@code ERA} field returns the value of the era. 224 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 225 * <p> 226 * If the field is not a {@code ChronoField}, then the result of this method 227 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} 228 * passing {@code this} as the argument. Whether the value can be obtained, 229 * and what the value represents, is determined by the field. 230 * 231 * @param field the field to get, not null 232 * @return the value for the field 233 * @throws DateTimeException if a value for the field cannot be obtained 234 * @throws UnsupportedTemporalTypeException if the field is not supported 235 * @throws ArithmeticException if numeric overflow occurs 236 */ 237 @Override 238 default long getLong(TemporalField field) { 239 if (field == ERA) { 240 return getValue(); 241 } else if (field instanceof ChronoField) { 242 throw new UnsupportedTemporalTypeException("Unsupported field: " + field); 243 } 244 return field.getFrom(this); 245 } 246 247 //----------------------------------------------------------------------- 248 /** 249 * Queries this era using the specified query. 250 * <p> 251 * This queries this era using the specified query strategy object. 252 * The {@code TemporalQuery} object defines the logic to be used to 253 * obtain the result. Read the documentation of the query to understand 254 * what the result of this method will be. 255 * <p> 256 * The result of this method is obtained by invoking the 257 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the 258 * specified query passing {@code this} as the argument. 259 * 260 * @param <R> the type of the result 261 * @param query the query to invoke, not null 262 * @return the query result, null may be returned (defined by the query) 263 * @throws DateTimeException if unable to query (defined by the query) 264 * @throws ArithmeticException if numeric overflow occurs (defined by the query) 265 */ 266 @SuppressWarnings("unchecked") 267 @Override 268 default <R> R query(TemporalQuery<R> query) { 269 if (query == TemporalQueries.precision()) { 270 return (R) ERAS; 271 } 272 return TemporalAccessor.super.query(query); 273 } 274 275 /** 276 * Adjusts the specified temporal object to have the same era as this object. 277 * <p> 278 * This returns a temporal object of the same observable type as the input 279 * with the era changed to be the same as this. 280 * <p> 281 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)} 282 * passing {@link ChronoField#ERA} as the field. 283 * <p> 284 * In most cases, it is clearer to reverse the calling pattern by using 285 * {@link Temporal#with(TemporalAdjuster)}: 286 * <pre> 287 * // these two lines are equivalent, but the second approach is recommended 288 * temporal = thisEra.adjustInto(temporal); 289 * temporal = temporal.with(thisEra); 290 * </pre> 291 * <p> 292 * This instance is immutable and unaffected by this method call. 293 * 294 * @param temporal the target object to be adjusted, not null 295 * @return the adjusted object, not null 296 * @throws DateTimeException if unable to make the adjustment 297 * @throws ArithmeticException if numeric overflow occurs 298 */ 299 @Override 300 default Temporal adjustInto(Temporal temporal) { 301 return temporal.with(ERA, getValue()); 302 } 303 304 //----------------------------------------------------------------------- 305 /** 306 * Gets the textual representation of this era. 307 * <p> 308 * This returns the textual name used to identify the era, 309 * suitable for presentation to the user. 310 * The parameters control the style of the returned text and the locale. 311 * <p> 312 * If no textual mapping is found then the {@link #getValue() numeric value} is returned. 313 * <p> 314 * This default implementation is suitable for all implementations. 315 * 316 * @param style the style of the text required, not null 317 * @param locale the locale to use, not null 318 * @return the text value of the era, not null 319 */ 320 default String getDisplayName(TextStyle style, Locale locale) { 321 return new DateTimeFormatterBuilder().appendText(ERA, style).toFormatter(locale).format(this); 322 } 323 324 // NOTE: methods to convert year-of-era/proleptic-year cannot be here as they may depend on month/day (Japanese) 325 } 326
