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

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     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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    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 }