Java tutorial
/* * Copyright (c) 2012, 2015, 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) 2012-2013, 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 static java.time.temporal.ChronoField.DAY_OF_MONTH; import static java.time.temporal.ChronoField.DAY_OF_WEEK; import static java.time.temporal.ChronoField.DAY_OF_YEAR; import static java.time.temporal.ChronoUnit.DAYS; import static java.time.temporal.ChronoUnit.MONTHS; import static java.time.temporal.ChronoUnit.YEARS; import java.time.DayOfWeek; import java.time.LocalDate; import java.util.Objects; import java.util.function.UnaryOperator; /** * Common and useful TemporalAdjusters. * <p> * Adjusters are a key tool for modifying temporal objects. * They exist to externalize the process of adjustment, permitting different * approaches, as per the strategy design pattern. * Examples might be an adjuster that sets the date avoiding weekends, or one that * sets the date to the last day of the month. * <p> * There are two equivalent ways of using a {@code TemporalAdjuster}. * The first is to invoke the method on the interface directly. * The second is to use {@link Temporal#with(TemporalAdjuster)}: * <pre> * // these two lines are equivalent, but the second approach is recommended * temporal = thisAdjuster.adjustInto(temporal); * temporal = temporal.with(thisAdjuster); * </pre> * It is recommended to use the second approach, {@code with(TemporalAdjuster)}, * as it is a lot clearer to read in code. * <p> * This class contains a standard set of adjusters, available as static methods. * These include: * <ul> * <li>finding the first or last day of the month * <li>finding the first day of next month * <li>finding the first or last day of the year * <li>finding the first day of next year * <li>finding the first or last day-of-week within a month, such as "first Wednesday in June" * <li>finding the next or previous day-of-week, such as "next Thursday" * </ul> * * @implSpec * All the implementations supplied by the static methods are immutable. * * @see TemporalAdjuster * @since 1.8 */ public final class TemporalAdjusters { /** * Private constructor since this is a utility class. */ private TemporalAdjusters() { } //----------------------------------------------------------------------- /** * Obtains a {@code TemporalAdjuster} that wraps a date adjuster. * <p> * The {@code TemporalAdjuster} is based on the low level {@code Temporal} interface. * This method allows an adjustment from {@code LocalDate} to {@code LocalDate} * to be wrapped to match the temporal-based interface. * This is provided for convenience to make user-written adjusters simpler. * <p> * In general, user-written adjusters should be static constants: * <pre>{@code * static TemporalAdjuster TWO_DAYS_LATER = * TemporalAdjusters.ofDateAdjuster(date -> date.plusDays(2)); * }</pre> * * @param dateBasedAdjuster the date-based adjuster, not null * @return the temporal adjuster wrapping on the date adjuster, not null */ public static TemporalAdjuster ofDateAdjuster(UnaryOperator<LocalDate> dateBasedAdjuster) { Objects.requireNonNull(dateBasedAdjuster, "dateBasedAdjuster"); return (temporal) -> { LocalDate input = LocalDate.from(temporal); LocalDate output = dateBasedAdjuster.apply(input); return temporal.with(output); }; } //----------------------------------------------------------------------- /** * Returns the "first day of month" adjuster, which returns a new date set to * the first day of the current month. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 will return 2011-01-01.<br> * The input 2011-02-15 will return 2011-02-01. * <p> * The behavior is suitable for use with most calendar systems. * It is equivalent to: * <pre> * temporal.with(DAY_OF_MONTH, 1); * </pre> * * @return the first day-of-month adjuster, not null */ public static TemporalAdjuster firstDayOfMonth() { return (temporal) -> temporal.with(DAY_OF_MONTH, 1); } /** * Returns the "last day of month" adjuster, which returns a new date set to * the last day of the current month. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 will return 2011-01-31.<br> * The input 2011-02-15 will return 2011-02-28.<br> * The input 2012-02-15 will return 2012-02-29 (leap year).<br> * The input 2011-04-15 will return 2011-04-30. * <p> * The behavior is suitable for use with most calendar systems. * It is equivalent to: * <pre> * long lastDay = temporal.range(DAY_OF_MONTH).getMaximum(); * temporal.with(DAY_OF_MONTH, lastDay); * </pre> * * @return the last day-of-month adjuster, not null */ public static TemporalAdjuster lastDayOfMonth() { return (temporal) -> temporal.with(DAY_OF_MONTH, temporal.range(DAY_OF_MONTH).getMaximum()); } /** * Returns the "first day of next month" adjuster, which returns a new date set to * the first day of the next month. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 will return 2011-02-01.<br> * The input 2011-02-15 will return 2011-03-01. * <p> * The behavior is suitable for use with most calendar systems. * It is equivalent to: * <pre> * temporal.with(DAY_OF_MONTH, 1).plus(1, MONTHS); * </pre> * * @return the first day of next month adjuster, not null */ public static TemporalAdjuster firstDayOfNextMonth() { return (temporal) -> temporal.with(DAY_OF_MONTH, 1).plus(1, MONTHS); } //----------------------------------------------------------------------- /** * Returns the "first day of year" adjuster, which returns a new date set to * the first day of the current year. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 will return 2011-01-01.<br> * The input 2011-02-15 will return 2011-01-01.<br> * <p> * The behavior is suitable for use with most calendar systems. * It is equivalent to: * <pre> * temporal.with(DAY_OF_YEAR, 1); * </pre> * * @return the first day-of-year adjuster, not null */ public static TemporalAdjuster firstDayOfYear() { return (temporal) -> temporal.with(DAY_OF_YEAR, 1); } /** * Returns the "last day of year" adjuster, which returns a new date set to * the last day of the current year. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 will return 2011-12-31.<br> * The input 2011-02-15 will return 2011-12-31.<br> * <p> * The behavior is suitable for use with most calendar systems. * It is equivalent to: * <pre> * long lastDay = temporal.range(DAY_OF_YEAR).getMaximum(); * temporal.with(DAY_OF_YEAR, lastDay); * </pre> * * @return the last day-of-year adjuster, not null */ public static TemporalAdjuster lastDayOfYear() { return (temporal) -> temporal.with(DAY_OF_YEAR, temporal.range(DAY_OF_YEAR).getMaximum()); } /** * Returns the "first day of next year" adjuster, which returns a new date set to * the first day of the next year. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 will return 2012-01-01. * <p> * The behavior is suitable for use with most calendar systems. * It is equivalent to: * <pre> * temporal.with(DAY_OF_YEAR, 1).plus(1, YEARS); * </pre> * * @return the first day of next month adjuster, not null */ public static TemporalAdjuster firstDayOfNextYear() { return (temporal) -> temporal.with(DAY_OF_YEAR, 1).plus(1, YEARS); } //----------------------------------------------------------------------- /** * Returns the first in month adjuster, which returns a new date * in the same month with the first matching day-of-week. * This is used for expressions like 'first Tuesday in March'. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-12-15 for (MONDAY) will return 2011-12-05.<br> * The input 2011-12-15 for (FRIDAY) will return 2011-12-02.<br> * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} and {@code DAY_OF_MONTH} fields * and the {@code DAYS} unit, and assumes a seven day week. * * @param dayOfWeek the day-of-week, not null * @return the first in month adjuster, not null */ public static TemporalAdjuster firstInMonth(DayOfWeek dayOfWeek) { return TemporalAdjusters.dayOfWeekInMonth(1, dayOfWeek); } /** * Returns the last in month adjuster, which returns a new date * in the same month with the last matching day-of-week. * This is used for expressions like 'last Tuesday in March'. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-12-15 for (MONDAY) will return 2011-12-26.<br> * The input 2011-12-15 for (FRIDAY) will return 2011-12-30.<br> * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} and {@code DAY_OF_MONTH} fields * and the {@code DAYS} unit, and assumes a seven day week. * * @param dayOfWeek the day-of-week, not null * @return the first in month adjuster, not null */ public static TemporalAdjuster lastInMonth(DayOfWeek dayOfWeek) { return TemporalAdjusters.dayOfWeekInMonth(-1, dayOfWeek); } /** * Returns the day-of-week in month adjuster, which returns a new date * with the ordinal day-of-week based on the month. * This is used for expressions like the 'second Tuesday in March'. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-12-15 for (1,TUESDAY) will return 2011-12-06.<br> * The input 2011-12-15 for (2,TUESDAY) will return 2011-12-13.<br> * The input 2011-12-15 for (3,TUESDAY) will return 2011-12-20.<br> * The input 2011-12-15 for (4,TUESDAY) will return 2011-12-27.<br> * The input 2011-12-15 for (5,TUESDAY) will return 2012-01-03.<br> * The input 2011-12-15 for (-1,TUESDAY) will return 2011-12-27 (last in month).<br> * The input 2011-12-15 for (-4,TUESDAY) will return 2011-12-06 (3 weeks before last in month).<br> * The input 2011-12-15 for (-5,TUESDAY) will return 2011-11-29 (4 weeks before last in month).<br> * The input 2011-12-15 for (0,TUESDAY) will return 2011-11-29 (last in previous month).<br> * <p> * For a positive or zero ordinal, the algorithm is equivalent to finding the first * day-of-week that matches within the month and then adding a number of weeks to it. * For a negative ordinal, the algorithm is equivalent to finding the last * day-of-week that matches within the month and then subtracting a number of weeks to it. * The ordinal number of weeks is not validated and is interpreted leniently * according to this algorithm. This definition means that an ordinal of zero finds * the last matching day-of-week in the previous month. * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} and {@code DAY_OF_MONTH} fields * and the {@code DAYS} unit, and assumes a seven day week. * * @param ordinal the week within the month, unbounded but typically from -5 to 5 * @param dayOfWeek the day-of-week, not null * @return the day-of-week in month adjuster, not null */ public static TemporalAdjuster dayOfWeekInMonth(int ordinal, DayOfWeek dayOfWeek) { Objects.requireNonNull(dayOfWeek, "dayOfWeek"); int dowValue = dayOfWeek.getValue(); if (ordinal >= 0) { return (temporal) -> { Temporal temp = temporal.with(DAY_OF_MONTH, 1); int curDow = temp.get(DAY_OF_WEEK); int dowDiff = (dowValue - curDow + 7) % 7; dowDiff += (ordinal - 1L) * 7L; // safe from overflow return temp.plus(dowDiff, DAYS); }; } else { return (temporal) -> { Temporal temp = temporal.with(DAY_OF_MONTH, temporal.range(DAY_OF_MONTH).getMaximum()); int curDow = temp.get(DAY_OF_WEEK); int daysDiff = dowValue - curDow; daysDiff = (daysDiff == 0 ? 0 : (daysDiff > 0 ? daysDiff - 7 : daysDiff)); daysDiff -= (-ordinal - 1L) * 7L; // safe from overflow return temp.plus(daysDiff, DAYS); }; } } //----------------------------------------------------------------------- /** * Returns the next day-of-week adjuster, which adjusts the date to the * first occurrence of the specified day-of-week after the date being adjusted. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-17 (two days later).<br> * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-19 (four days later).<br> * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-22 (seven days later). * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit, * and assumes a seven day week. * * @param dayOfWeek the day-of-week to move the date to, not null * @return the next day-of-week adjuster, not null */ public static TemporalAdjuster next(DayOfWeek dayOfWeek) { int dowValue = dayOfWeek.getValue(); return (temporal) -> { int calDow = temporal.get(DAY_OF_WEEK); int daysDiff = calDow - dowValue; return temporal.plus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS); }; } /** * Returns the next-or-same day-of-week adjuster, which adjusts the date to the * first occurrence of the specified day-of-week after the date being adjusted * unless it is already on that day in which case the same object is returned. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-17 (two days later).<br> * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-19 (four days later).<br> * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-15 (same as input). * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit, * and assumes a seven day week. * * @param dayOfWeek the day-of-week to check for or move the date to, not null * @return the next-or-same day-of-week adjuster, not null */ public static TemporalAdjuster nextOrSame(DayOfWeek dayOfWeek) { int dowValue = dayOfWeek.getValue(); return (temporal) -> { int calDow = temporal.get(DAY_OF_WEEK); if (calDow == dowValue) { return temporal; } int daysDiff = calDow - dowValue; return temporal.plus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS); }; } /** * Returns the previous day-of-week adjuster, which adjusts the date to the * first occurrence of the specified day-of-week before the date being adjusted. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-10 (five days earlier).<br> * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-12 (three days earlier).<br> * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-08 (seven days earlier). * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit, * and assumes a seven day week. * * @param dayOfWeek the day-of-week to move the date to, not null * @return the previous day-of-week adjuster, not null */ public static TemporalAdjuster previous(DayOfWeek dayOfWeek) { int dowValue = dayOfWeek.getValue(); return (temporal) -> { int calDow = temporal.get(DAY_OF_WEEK); int daysDiff = dowValue - calDow; return temporal.minus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS); }; } /** * Returns the previous-or-same day-of-week adjuster, which adjusts the date to the * first occurrence of the specified day-of-week before the date being adjusted * unless it is already on that day in which case the same object is returned. * <p> * The ISO calendar system behaves as follows:<br> * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-10 (five days earlier).<br> * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-12 (three days earlier).<br> * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-15 (same as input). * <p> * The behavior is suitable for use with most calendar systems. * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit, * and assumes a seven day week. * * @param dayOfWeek the day-of-week to check for or move the date to, not null * @return the previous-or-same day-of-week adjuster, not null */ public static TemporalAdjuster previousOrSame(DayOfWeek dayOfWeek) { int dowValue = dayOfWeek.getValue(); return (temporal) -> { int calDow = temporal.get(DAY_OF_WEEK); if (calDow == dowValue) { return temporal; } int daysDiff = dowValue - calDow; return temporal.minus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS); }; } }