Java tutorial
/* * Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * * Neither the name of JSR-310 nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package java.time.temporal; import java.time.DateTimeException; /** * Framework-level interface defining read-write access to a temporal object, * such as a date, time, offset or some combination of these. * <p> * This is the base interface type for date, time and offset objects that * are complete enough to be manipulated using plus and minus. * It is implemented by those classes that can provide and manipulate information * as {@linkplain TemporalField fields} or {@linkplain TemporalQuery queries}. * See {@link TemporalAccessor} for the read-only version of this interface. * <p> * Most date and time information can be represented as a number. * These are modeled using {@code TemporalField} with the number held using * a {@code long} to handle large values. Year, month and day-of-month are * simple examples of fields, but they also include instant and offsets. * See {@link ChronoField} for the standard set of fields. * <p> * Two pieces of date/time information cannot be represented by numbers, * the {@linkplain java.time.chrono.Chronology chronology} and the * {@linkplain java.time.ZoneId time-zone}. * These can be accessed via {@link #query(TemporalQuery) queries} using * the static methods defined on {@link TemporalQuery}. * <p> * This interface is a framework-level interface that should not be widely * used in application code. Instead, applications should create and pass * around instances of concrete types, such as {@code LocalDate}. * There are many reasons for this, part of which is that implementations * of this interface may be in calendar systems other than ISO. * See {@link java.time.chrono.ChronoLocalDate} for a fuller discussion of the issues. * * <h2>When to implement</h2> * <p> * A class should implement this interface if it meets three criteria: * <ul> * <li>it provides access to date/time/offset information, as per {@code TemporalAccessor} * <li>the set of fields are contiguous from the largest to the smallest * <li>the set of fields are complete, such that no other field is needed to define the * valid range of values for the fields that are represented * </ul> * <p> * Four examples make this clear: * <ul> * <li>{@code LocalDate} implements this interface as it represents a set of fields * that are contiguous from days to forever and require no external information to determine * the validity of each date. It is therefore able to implement plus/minus correctly. * <li>{@code LocalTime} implements this interface as it represents a set of fields * that are contiguous from nanos to within days and require no external information to determine * validity. It is able to implement plus/minus correctly, by wrapping around the day. * <li>{@code MonthDay}, the combination of month-of-year and day-of-month, does not implement * this interface. While the combination is contiguous, from days to months within years, * the combination does not have sufficient information to define the valid range of values * for day-of-month. As such, it is unable to implement plus/minus correctly. * <li>The combination day-of-week and day-of-month ("Friday the 13th") should not implement * this interface. It does not represent a contiguous set of fields, as days to weeks overlaps * days to months. * </ul> * * @implSpec * This interface places no restrictions on the mutability of implementations, * however immutability is strongly recommended. * All implementations must be {@link Comparable}. * * @since 1.8 */ public interface Temporal extends TemporalAccessor { /** * Checks if the specified unit is supported. * <p> * This checks if the specified unit can be added to, or subtracted from, this date-time. * If false, then calling the {@link #plus(long, TemporalUnit)} and * {@link #minus(long, TemporalUnit) minus} methods will throw an exception. * * @implSpec * Implementations must check and handle all units defined in {@link ChronoUnit}. * If the unit is supported, then true must be returned, otherwise false must be returned. * <p> * If the field is not a {@code ChronoUnit}, then the result of this method * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)} * passing {@code this} as the argument. * <p> * Implementations must ensure that no observable state is altered when this * read-only method is invoked. * * @param unit the unit to check, null returns false * @return true if the unit can be added/subtracted, false if not */ boolean isSupported(TemporalUnit unit); /** * Returns an adjusted object of the same type as this object with the adjustment made. * <p> * This adjusts this date-time according to the rules of the specified adjuster. * A simple adjuster might simply set the one of the fields, such as the year field. * A more complex adjuster might set the date to the last day of the month. * A selection of common adjustments is provided in * {@link java.time.temporal.TemporalAdjusters TemporalAdjusters}. * These include finding the "last day of the month" and "next Wednesday". * The adjuster is responsible for handling special cases, such as the varying * lengths of month and leap years. * <p> * Some example code indicating how and why this method is used: * <pre> * date = date.with(Month.JULY); // most key classes implement TemporalAdjuster * date = date.with(lastDayOfMonth()); // static import from Adjusters * date = date.with(next(WEDNESDAY)); // static import from Adjusters and DayOfWeek * </pre> * * @implSpec * <p> * Implementations must not alter either this object or the specified temporal object. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable implementations. * <p> * The default implementation must behave equivalent to this code: * <pre> * return adjuster.adjustInto(this); * </pre> * * @param adjuster the adjuster to use, not null * @return an object of the same type with the specified adjustment made, not null * @throws DateTimeException if unable to make the adjustment * @throws ArithmeticException if numeric overflow occurs */ default Temporal with(TemporalAdjuster adjuster) { return adjuster.adjustInto(this); } /** * Returns an object of the same type as this object with the specified field altered. * <p> * This returns a new object based on this one with the value for the specified field changed. * For example, on a {@code LocalDate}, this could be used to set the year, month or day-of-month. * The returned object will have the same observable type as this object. * <p> * In some cases, changing a field is not fully defined. For example, if the target object is * a date representing the 31st January, then changing the month to February would be unclear. * In cases like this, the field is responsible for resolving the result. Typically it will choose * the previous valid date, which would be the last valid day of February in this example. * * @implSpec * Implementations must check and handle all fields defined in {@link ChronoField}. * If the field is supported, then the adjustment must be performed. * If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown. * <p> * If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)} * passing {@code this} as the first argument. * <p> * Implementations must not alter this object. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable implementations. * * @param field the field to set in the result, not null * @param newValue the new value of the field in the result * @return an object of the same type with the specified field set, not null * @throws DateTimeException if the field cannot be set * @throws UnsupportedTemporalTypeException if the field is not supported * @throws ArithmeticException if numeric overflow occurs */ Temporal with(TemporalField field, long newValue); //----------------------------------------------------------------------- /** * Returns an object of the same type as this object with an amount added. * <p> * This adjusts this temporal, adding according to the rules of the specified amount. * The amount is typically a {@link java.time.Period} but may be any other type implementing * the {@link TemporalAmount} interface, such as {@link java.time.Duration}. * <p> * Some example code indicating how and why this method is used: * <pre> * date = date.plus(period); // add a Period instance * date = date.plus(duration); // add a Duration instance * date = date.plus(workingDays(6)); // example user-written workingDays method * </pre> * <p> * Note that calling {@code plus} followed by {@code minus} is not guaranteed to * return the same date-time. * * @implSpec * <p> * Implementations must not alter either this object or the specified temporal object. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable implementations. * <p> * The default implementation must behave equivalent to this code: * <pre> * return amount.addTo(this); * </pre> * * @param amount the amount to add, not null * @return an object of the same type with the specified adjustment made, not null * @throws DateTimeException if the addition cannot be made * @throws ArithmeticException if numeric overflow occurs */ default Temporal plus(TemporalAmount amount) { return amount.addTo(this); } /** * Returns an object of the same type as this object with the specified period added. * <p> * This method returns a new object based on this one with the specified period added. * For example, on a {@code LocalDate}, this could be used to add a number of years, months or days. * The returned object will have the same observable type as this object. * <p> * In some cases, changing a field is not fully defined. For example, if the target object is * a date representing the 31st January, then adding one month would be unclear. * In cases like this, the field is responsible for resolving the result. Typically it will choose * the previous valid date, which would be the last valid day of February in this example. * * @implSpec * Implementations must check and handle all units defined in {@link ChronoUnit}. * If the unit is supported, then the addition must be performed. * If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown. * <p> * If the unit is not a {@code ChronoUnit}, then the result of this method * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)} * passing {@code this} as the first argument. * <p> * Implementations must not alter this object. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable implementations. * * @param amountToAdd the amount of the specified unit to add, may be negative * @param unit the unit of the amount to add, not null * @return an object of the same type with the specified period added, not null * @throws DateTimeException if the unit cannot be added * @throws UnsupportedTemporalTypeException if the unit is not supported * @throws ArithmeticException if numeric overflow occurs */ Temporal plus(long amountToAdd, TemporalUnit unit); //----------------------------------------------------------------------- /** * Returns an object of the same type as this object with an amount subtracted. * <p> * This adjusts this temporal, subtracting according to the rules of the specified amount. * The amount is typically a {@link java.time.Period} but may be any other type implementing * the {@link TemporalAmount} interface, such as {@link java.time.Duration}. * <p> * Some example code indicating how and why this method is used: * <pre> * date = date.minus(period); // subtract a Period instance * date = date.minus(duration); // subtract a Duration instance * date = date.minus(workingDays(6)); // example user-written workingDays method * </pre> * <p> * Note that calling {@code plus} followed by {@code minus} is not guaranteed to * return the same date-time. * * @implSpec * <p> * Implementations must not alter either this object or the specified temporal object. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable implementations. * <p> * The default implementation must behave equivalent to this code: * <pre> * return amount.subtractFrom(this); * </pre> * * @param amount the amount to subtract, not null * @return an object of the same type with the specified adjustment made, not null * @throws DateTimeException if the subtraction cannot be made * @throws ArithmeticException if numeric overflow occurs */ default Temporal minus(TemporalAmount amount) { return amount.subtractFrom(this); } /** * Returns an object of the same type as this object with the specified period subtracted. * <p> * This method returns a new object based on this one with the specified period subtracted. * For example, on a {@code LocalDate}, this could be used to subtract a number of years, months or days. * The returned object will have the same observable type as this object. * <p> * In some cases, changing a field is not fully defined. For example, if the target object is * a date representing the 31st March, then subtracting one month would be unclear. * In cases like this, the field is responsible for resolving the result. Typically it will choose * the previous valid date, which would be the last valid day of February in this example. * * @implSpec * Implementations must behave in a manor equivalent to the default method behavior. * <p> * Implementations must not alter this object. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable implementations. * <p> * The default implementation must behave equivalent to this code: * <pre> * return (amountToSubtract == Long.MIN_VALUE ? * plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit)); * </pre> * * @param amountToSubtract the amount of the specified unit to subtract, may be negative * @param unit the unit of the amount to subtract, not null * @return an object of the same type with the specified period subtracted, not null * @throws DateTimeException if the unit cannot be subtracted * @throws UnsupportedTemporalTypeException if the unit is not supported * @throws ArithmeticException if numeric overflow occurs */ default Temporal minus(long amountToSubtract, TemporalUnit unit) { return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit)); } //----------------------------------------------------------------------- /** * Calculates the amount of time until another temporal in terms of the specified unit. * <p> * This calculates the amount of time between two temporal objects * in terms of a single {@code TemporalUnit}. * The start and end points are {@code this} and the specified temporal. * The end point is converted to be of the same type as the start point if different. * The result will be negative if the end is before the start. * For example, the amount in hours between two temporal objects can be * calculated using {@code startTime.until(endTime, HOURS)}. * <p> * The calculation returns a whole number, representing the number of * complete units between the two temporals. * For example, the amount in hours between the times 11:30 and 13:29 * will only be one hour as it is one minute short of two hours. * <p> * There are two equivalent ways of using this method. * The first is to invoke this method directly. * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}: * <pre> * // these two lines are equivalent * temporal = start.until(end, unit); * temporal = unit.between(start, end); * </pre> * The choice should be made based on which makes the code more readable. * <p> * For example, this method allows the number of days between two dates to * be calculated: * <pre> * long daysBetween = start.until(end, DAYS); * // or alternatively * long daysBetween = DAYS.between(start, end); * </pre> * * @implSpec * Implementations must begin by checking to ensure that the input temporal * object is of the same observable type as the implementation. * They must then perform the calculation for all instances of {@link ChronoUnit}. * An {@code UnsupportedTemporalTypeException} must be thrown for {@code ChronoUnit} * instances that are unsupported. * <p> * If the unit is not a {@code ChronoUnit}, then the result of this method * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)} * passing {@code this} as the first argument and the converted input temporal as * the second argument. * <p> * In summary, implementations must behave in a manner equivalent to this pseudo-code: * <pre> * // convert the end temporal to the same type as this class * if (unit instanceof ChronoUnit) { * // if unit is supported, then calculate and return result * // else throw UnsupportedTemporalTypeException for unsupported units * } * return unit.between(this, convertedEndTemporal); * </pre> * <p> * Note that the unit's {@code between} method must only be invoked if the * two temporal objects have exactly the same type evaluated by {@code getClass()}. * <p> * Implementations must ensure that no observable state is altered when this * read-only method is invoked. * * @param endExclusive the end temporal, exclusive, converted to be of the * same type as this object, not null * @param unit the unit to measure the amount in, not null * @return the amount of time between this temporal object and the specified one * in terms of the unit; positive if the specified object is later than this one, * negative if it is earlier than this one * @throws DateTimeException if the amount cannot be calculated, or the end * temporal cannot be converted to the same type as this temporal * @throws UnsupportedTemporalTypeException if the unit is not supported * @throws ArithmeticException if numeric overflow occurs */ long until(Temporal endExclusive, TemporalUnit unit); }