src/share/classes/java/time/temporal/TemporalQuery.java

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  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 
  66 /**
  67  * Strategy for querying a temporal object.
  68  * <p>
  69  * Queries are a key tool for extracting information from temporal objects.
  70  * They exist to externalize the process of querying, permitting different
  71  * approaches, as per the strategy design pattern.
  72  * Examples might be a query that checks if the date is the day before February 29th
  73  * in a leap year, or calculates the number of days to your next birthday.
  74  * <p>
  75  * The {@link TemporalField} interface provides another mechanism for querying
  76  * temporal objects. That interface is limited to returning a {@code long}.
  77  * By contrast, queries can return any type.
  78  * <p>
  79  * There are two equivalent ways of using a {@code TemporalQuery}.
  80  * The first is to invoke the method on this interface directly.
  81  * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
  82  * <pre>
  83  *   // these two lines are equivalent, but the second approach is recommended
  84  *   temporal = thisQuery.queryFrom(temporal);
  85  *   temporal = temporal.query(thisQuery);
  86  * </pre>
  87  * It is recommended to use the second approach, {@code query(TemporalQuery)},
  88  * as it is a lot clearer to read in code.
  89  * <p>
  90  * The most common implementations are method references, such as
  91  * {@code LocalDate::from} and {@code ZoneId::from}.
  92  * Further implementations are on {@link Queries}.
  93  * Queries may also be defined by applications.
  94  *
  95  * <h3>Specification for implementors</h3>
  96  * This interface places no restrictions on the mutability of implementations,
  97  * however immutability is strongly recommended.
  98  *
  99  * @since 1.8
 100  */
 101 @FunctionalInterface
 102 public interface TemporalQuery<R> {
 103 
 104     /**
 105      * Queries the specified temporal object.
 106      * <p>
 107      * This queries the specified temporal object to return an object using the logic
 108      * encapsulated in the implementing class.
 109      * Examples might be a query that checks if the date is the day before February 29th
 110      * in a leap year, or calculates the number of days to your next birthday.
 111      * <p>
 112      * There are two equivalent ways of using this method.
 113      * The first is to invoke this method directly.
 114      * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
 115      * <pre>
 116      *   // these two lines are equivalent, but the second approach is recommended
 117      *   temporal = thisQuery.queryFrom(temporal);
 118      *   temporal = temporal.query(thisQuery);
 119      * </pre>
 120      * It is recommended to use the second approach, {@code query(TemporalQuery)},
 121      * as it is a lot clearer to read in code.
 122      *
 123      * <h3>Specification for implementors</h3>
 124      * The implementation must take the input object and query it.
 125      * The implementation defines the logic of the query and is responsible for
 126      * documenting that logic.
 127      * It may use any method on {@code TemporalAccessor} to determine the result.
 128      * The input object must not be altered.
 129      * <p>
 130      * The input temporal object may be in a calendar system other than ISO.
 131      * Implementations may choose to document compatibility with other calendar systems,
 132      * or reject non-ISO temporal objects by {@link Queries#chronology() querying the chronology}.
 133      * <p>
 134      * This method may be called from multiple threads in parallel.
 135      * It must be thread-safe when invoked.
 136      *
 137      * @param temporal  the temporal object to query, not null
 138      * @return the queried value, may return null to indicate not found
 139      * @throws DateTimeException if unable to query
 140      * @throws ArithmeticException if numeric overflow occurs
 141      */
 142     R queryFrom(TemporalAccessor temporal);
 143 


















































































































































































































 144 }


  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.LocalDate;
  66 import java.time.LocalTime;
  67 import java.time.ZoneId;
  68 import java.time.ZoneOffset;
  69 import java.time.chrono.Chronology;
  70 
  71 /**
  72  * Strategy for querying a temporal object.
  73  * <p>
  74  * Queries are a key tool for extracting information from temporal objects.
  75  * They exist to externalize the process of querying, permitting different
  76  * approaches, as per the strategy design pattern.
  77  * Examples might be a query that checks if the date is the day before February 29th
  78  * in a leap year, or calculates the number of days to your next birthday.
  79  * <p>
  80  * The {@link TemporalField} interface provides another mechanism for querying
  81  * temporal objects. That interface is limited to returning a {@code long}.
  82  * By contrast, queries can return any type.
  83  * <p>
  84  * There are two equivalent ways of using a {@code TemporalQuery}.
  85  * The first is to invoke the method on this interface directly.
  86  * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
  87  * <pre>
  88  *   // these two lines are equivalent, but the second approach is recommended
  89  *   temporal = thisQuery.queryFrom(temporal);
  90  *   temporal = temporal.query(thisQuery);
  91  * </pre>
  92  * It is recommended to use the second approach, {@code query(TemporalQuery)},
  93  * as it is a lot clearer to read in code.
  94  * <p>
  95  * The most common implementations are method references, such as
  96  * {@code LocalDate::from} and {@code ZoneId::from}.
  97  * Additional common implementations are provided on this interface as static methods.

  98  *
  99  * <h3>Specification for implementors</h3>
 100  * This interface places no restrictions on the mutability of implementations,
 101  * however immutability is strongly recommended.
 102  *
 103  * @since 1.8
 104  */
 105 @FunctionalInterface
 106 public interface TemporalQuery<R> {
 107 
 108     /**
 109      * Queries the specified temporal object.
 110      * <p>
 111      * This queries the specified temporal object to return an object using the logic
 112      * encapsulated in the implementing class.
 113      * Examples might be a query that checks if the date is the day before February 29th
 114      * in a leap year, or calculates the number of days to your next birthday.
 115      * <p>
 116      * There are two equivalent ways of using this method.
 117      * The first is to invoke this method directly.
 118      * The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
 119      * <pre>
 120      *   // these two lines are equivalent, but the second approach is recommended
 121      *   temporal = thisQuery.queryFrom(temporal);
 122      *   temporal = temporal.query(thisQuery);
 123      * </pre>
 124      * It is recommended to use the second approach, {@code query(TemporalQuery)},
 125      * as it is a lot clearer to read in code.
 126      *
 127      * <h3>Specification for implementors</h3>
 128      * The implementation must take the input object and query it.
 129      * The implementation defines the logic of the query and is responsible for
 130      * documenting that logic.
 131      * It may use any method on {@code TemporalAccessor} to determine the result.
 132      * The input object must not be altered.
 133      * <p>
 134      * The input temporal object may be in a calendar system other than ISO.
 135      * Implementations may choose to document compatibility with other calendar systems,
 136      * or reject non-ISO temporal objects by {@link TemporalQuery#chronology() querying the chronology}.
 137      * <p>
 138      * This method may be called from multiple threads in parallel.
 139      * It must be thread-safe when invoked.
 140      *
 141      * @param temporal  the temporal object to query, not null
 142      * @return the queried value, may return null to indicate not found
 143      * @throws DateTimeException if unable to query
 144      * @throws ArithmeticException if numeric overflow occurs
 145      */
 146     R queryFrom(TemporalAccessor temporal);
 147 
 148     //-----------------------------------------------------------------------
 149     // special constants should be used to extract information from a TemporalAccessor
 150     // that cannot be derived in other ways
 151     // Javadoc added here, so as to pretend they are more normal than they really are
 152 
 153     /**
 154      * A strict query for the {@code ZoneId}.
 155      * <p>
 156      * This queries a {@code TemporalAccessor} for the zone.
 157      * The zone is only returned if the date-time conceptually contains a {@code ZoneId}.
 158      * It will not be returned if the date-time only conceptually has an {@code ZoneOffset}.
 159      * Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()},
 160      * but an {@link java.time.OffsetDateTime} will return null.
 161      * <p>
 162      * In most cases, applications should use {@link #zone()} as this query is too strict.
 163      * <p>
 164      * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>
 165      * {@code LocalDate} returns null<br>
 166      * {@code LocalTime} returns null<br>
 167      * {@code LocalDateTime} returns null<br>
 168      * {@code ZonedDateTime} returns the associated zone<br>
 169      * {@code OffsetTime} returns null<br>
 170      * {@code OffsetDateTime} returns null<br>
 171      * {@code ChronoLocalDate} returns null<br>
 172      * {@code ChronoLocalDateTime} returns null<br>
 173      * {@code ChronoZonedDateTime} returns the associated zone<br>
 174      * {@code Era} returns null<br>
 175      * {@code DayOfWeek} returns null<br>
 176      * {@code Month} returns null<br>
 177      * {@code Year} returns null<br>
 178      * {@code YearMonth} returns null<br>
 179      * {@code MonthDay} returns null<br>
 180      * {@code ZoneOffset} returns null<br>
 181      * {@code Instant} returns null<br>
 182      *
 183      * @return a query that can obtain the zone ID of a temporal, not null
 184      */
 185     static TemporalQuery<ZoneId> zoneId() {
 186         return TemporalQueries.ZONE_ID;
 187     }
 188 
 189     /**
 190      * A query for the {@code Chronology}.
 191      * <p>
 192      * This queries a {@code TemporalAccessor} for the chronology.
 193      * If the target {@code TemporalAccessor} represents a date, or part of a date,
 194      * then it should return the chronology that the date is expressed in.
 195      * As a result of this definition, objects only representing time, such as
 196      * {@code LocalTime}, will return null.
 197      * <p>
 198      * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>
 199      * {@code LocalDate} returns {@code IsoChronology.INSTANCE}<br>
 200      * {@code LocalTime} returns null (does not represent a date)<br>
 201      * {@code LocalDateTime} returns {@code IsoChronology.INSTANCE}<br>
 202      * {@code ZonedDateTime} returns {@code IsoChronology.INSTANCE}<br>
 203      * {@code OffsetTime} returns null (does not represent a date)<br>
 204      * {@code OffsetDateTime} returns {@code IsoChronology.INSTANCE}<br>
 205      * {@code ChronoLocalDate} returns the associated chronology<br>
 206      * {@code ChronoLocalDateTime} returns the associated chronology<br>
 207      * {@code ChronoZonedDateTime} returns the associated chronology<br>
 208      * {@code Era} returns the associated chronology<br>
 209      * {@code DayOfWeek} returns null (shared across chronologies)<br>
 210      * {@code Month} returns {@code IsoChronology.INSTANCE}<br>
 211      * {@code Year} returns {@code IsoChronology.INSTANCE}<br>
 212      * {@code YearMonth} returns {@code IsoChronology.INSTANCE}<br>
 213      * {@code MonthDay} returns null {@code IsoChronology.INSTANCE}<br>
 214      * {@code ZoneOffset} returns null (does not represent a date)<br>
 215      * {@code Instant} returns null (does not represent a date)<br>
 216      * <p>
 217      * The method {@link java.time.chrono.Chronology#from(TemporalAccessor)} can be used as a
 218      * {@code TemporalQuery} via a method reference, {@code Chronology::from}.
 219      * That method is equivalent to this query, except that it throws an
 220      * exception if a chronology cannot be obtained.
 221      *
 222      * @return a query that can obtain the chronology of a temporal, not null
 223      */
 224     static TemporalQuery<Chronology> chronology() {
 225         return TemporalQueries.CHRONO;
 226     }
 227 
 228     /**
 229      * A query for the smallest supported unit.
 230      * <p>
 231      * This queries a {@code TemporalAccessor} for the time precision.
 232      * If the target {@code TemporalAccessor} represents a consistent or complete date-time,
 233      * date or time then this must return the smallest precision actually supported.
 234      * Note that fields such as {@code NANO_OF_DAY} and {@code NANO_OF_SECOND}
 235      * are defined to always return ignoring the precision, thus this is the only
 236      * way to find the actual smallest supported unit.
 237      * For example, were {@code GregorianCalendar} to implement {@code TemporalAccessor}
 238      * it would return a precision of {@code MILLIS}.
 239      * <p>
 240      * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>
 241      * {@code LocalDate} returns {@code DAYS}<br>
 242      * {@code LocalTime} returns {@code NANOS}<br>
 243      * {@code LocalDateTime} returns {@code NANOS}<br>
 244      * {@code ZonedDateTime} returns {@code NANOS}<br>
 245      * {@code OffsetTime} returns {@code NANOS}<br>
 246      * {@code OffsetDateTime} returns {@code NANOS}<br>
 247      * {@code ChronoLocalDate} returns {@code DAYS}<br>
 248      * {@code ChronoLocalDateTime} returns {@code NANOS}<br>
 249      * {@code ChronoZonedDateTime} returns {@code NANOS}<br>
 250      * {@code Era} returns {@code ERAS}<br>
 251      * {@code DayOfWeek} returns {@code DAYS}<br>
 252      * {@code Month} returns {@code MONTHS}<br>
 253      * {@code Year} returns {@code YEARS}<br>
 254      * {@code YearMonth} returns {@code MONTHS}<br>
 255      * {@code MonthDay} returns null (does not represent a complete date or time)<br>
 256      * {@code ZoneOffset} returns null (does not represent a date or time)<br>
 257      * {@code Instant} returns {@code NANOS}<br>
 258      *
 259      * @return a query that can obtain the precision of a temporal, not null
 260      */
 261     static TemporalQuery<TemporalUnit> precision() {
 262         return TemporalQueries.PRECISION;
 263     }
 264 
 265     //-----------------------------------------------------------------------
 266     // non-special constants are standard queries that derive information from other information
 267     /**
 268      * A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}.
 269      * <p>
 270      * This queries a {@code TemporalAccessor} for the zone.
 271      * It first tries to obtain the zone, using {@link #zoneId()}.
 272      * If that is not found it tries to obtain the {@link #offset()}.
 273      * Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()},
 274      * while an {@link java.time.OffsetDateTime} will return the result of {@code getOffset()}.
 275      * <p>
 276      * In most cases, applications should use this query rather than {@code #zoneId()}.
 277      * <p>
 278      * The method {@link ZoneId#from(TemporalAccessor)} can be used as a
 279      * {@code TemporalQuery} via a method reference, {@code ZoneId::from}.
 280      * That method is equivalent to this query, except that it throws an
 281      * exception if a zone cannot be obtained.
 282      *
 283      * @return a query that can obtain the zone ID or offset of a temporal, not null
 284      */
 285     static TemporalQuery<ZoneId> zone() {
 286         return TemporalQueries.ZONE;
 287     }
 288 
 289     /**
 290      * A query for {@code ZoneOffset} returning null if not found.
 291      * <p>
 292      * This returns a {@code TemporalQuery} that can be used to query a temporal
 293      * object for the offset. The query will return null if the temporal
 294      * object cannot supply an offset.
 295      * <p>
 296      * The query implementation examines the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS}
 297      * field and uses it to create a {@code ZoneOffset}.
 298      * <p>
 299      * The method {@link java.time.ZoneOffset#from(TemporalAccessor)} can be used as a
 300      * {@code TemporalQuery} via a method reference, {@code ZoneOffset::from}.
 301      * This query and {@code ZoneOffset::from} will return the same result if the
 302      * temporal object contains an offset. If the temporal object does not contain
 303      * an offset, then the method reference will throw an exception, whereas this
 304      * query will return null.
 305      *
 306      * @return a query that can obtain the offset of a temporal, not null
 307      */
 308     static TemporalQuery<ZoneOffset> offset() {
 309         return TemporalQueries.OFFSET;
 310     }
 311 
 312     /**
 313      * A query for {@code LocalDate} returning null if not found.
 314      * <p>
 315      * This returns a {@code TemporalQuery} that can be used to query a temporal
 316      * object for the local date. The query will return null if the temporal
 317      * object cannot supply a local date.
 318      * <p>
 319      * The query implementation examines the {@link ChronoField#EPOCH_DAY EPOCH_DAY}
 320      * field and uses it to create a {@code LocalDate}.
 321      * <p>
 322      * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a
 323      * {@code TemporalQuery} via a method reference, {@code LocalDate::from}.
 324      * This query and {@code LocalDate::from} will return the same result if the
 325      * temporal object contains a date. If the temporal object does not contain
 326      * a date, then the method reference will throw an exception, whereas this
 327      * query will return null.
 328      *
 329      * @return a query that can obtain the date of a temporal, not null
 330      */
 331     static TemporalQuery<LocalDate> localDate() {
 332         return TemporalQueries.LOCAL_DATE;
 333     }
 334 
 335     /**
 336      * A query for {@code LocalTime} returning null if not found.
 337      * <p>
 338      * This returns a {@code TemporalQuery} that can be used to query a temporal
 339      * object for the local time. The query will return null if the temporal
 340      * object cannot supply a local time.
 341      * <p>
 342      * The query implementation examines the {@link ChronoField#NANO_OF_DAY NANO_OF_DAY}
 343      * field and uses it to create a {@code LocalTime}.
 344      * <p>
 345      * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a
 346      * {@code TemporalQuery} via a method reference, {@code LocalTime::from}.
 347      * This query and {@code LocalTime::from} will return the same result if the
 348      * temporal object contains a time. If the temporal object does not contain
 349      * a time, then the method reference will throw an exception, whereas this
 350      * query will return null.
 351      *
 352      * @return a query that can obtain the time of a temporal, not null
 353      */
 354     static TemporalQuery<LocalTime> localTime() {
 355         return TemporalQueries.LOCAL_TIME;
 356     }
 357 
 358 }