Java tutorial
/* * Copyright (c) 2012, 2013, 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 java.time.DateTimeException; import java.time.Duration; import java.time.Period; import java.util.List; /** * Framework-level interface defining an amount of time, such as * "6 hours", "8 days" or "2 years and 3 months". * <p> * This is the base interface type for amounts of time. * An amount is distinct from a date or time-of-day in that it is not tied * to any specific point on the time-line. * <p> * The amount can be thought of as a {@code Map} of {@link TemporalUnit} to * {@code long}, exposed via {@link #getUnits()} and {@link #get(TemporalUnit)}. * A simple case might have a single unit-value pair, such as "6 hours". * A more complex case may have multiple unit-value pairs, such as * "7 years, 3 months and 5 days". * <p> * There are two common implementations. * {@link Period} is a date-based implementation, storing years, months and days. * {@link Duration} is a time-based implementation, storing seconds and nanoseconds, * but providing some access using other duration based units such as minutes, * hours and fixed 24-hour days. * <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 Period} and {@code Duration}. * * @implSpec * This interface places no restrictions on the mutability of implementations, * however immutability is strongly recommended. * * @since 1.8 */ public interface TemporalAmount { /** * Returns the value of the requested unit. * The units returned from {@link #getUnits()} uniquely define the * value of the {@code TemporalAmount}. A value must be returned * for each unit listed in {@code getUnits}. * * @implSpec * Implementations may declare support for units not listed by {@link #getUnits()}. * Typically, the implementation would define additional units * as conversions for the convenience of developers. * * @param unit the {@code TemporalUnit} for which to return the value * @return the long value of the unit * @throws DateTimeException if a value for the unit cannot be obtained * @throws UnsupportedTemporalTypeException if the {@code unit} is not supported */ long get(TemporalUnit unit); /** * Returns the list of units uniquely defining the value of this TemporalAmount. * The list of {@code TemporalUnits} is defined by the implementation class. * The list is a snapshot of the units at the time {@code getUnits} * is called and is not mutable. * The units are ordered from longest duration to the shortest duration * of the unit. * * @implSpec * The list of units completely and uniquely represents the * state of the object without omissions, overlaps or duplication. * The units are in order from longest duration to shortest. * * @return the List of {@code TemporalUnits}; not null */ List<TemporalUnit> getUnits(); /** * Adds to the specified temporal object. * <p> * Adds the amount to the specified temporal object using the logic * encapsulated in the implementing class. * <p> * There are two equivalent ways of using this method. * The first is to invoke this method directly. * The second is to use {@link Temporal#plus(TemporalAmount)}: * <pre> * // These two lines are equivalent, but the second approach is recommended * dateTime = amount.addTo(dateTime); * dateTime = dateTime.plus(adder); * </pre> * It is recommended to use the second approach, {@code plus(TemporalAmount)}, * as it is a lot clearer to read in code. * * @implSpec * The implementation must take the input object and add to it. * The implementation defines the logic of the addition and is responsible for * documenting that logic. It may use any method on {@code Temporal} to * query the temporal object and perform the addition. * The returned object must have the same observable type as the input object * <p> * The input object must not be altered. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable temporal objects. * <p> * The input temporal object may be in a calendar system other than ISO. * Implementations may choose to document compatibility with other calendar systems, * or reject non-ISO temporal objects by {@link TemporalQueries#chronology() querying the chronology}. * <p> * This method may be called from multiple threads in parallel. * It must be thread-safe when invoked. * * @param temporal the temporal object to add the amount to, not null * @return an object of the same observable type with the addition made, not null * @throws DateTimeException if unable to add * @throws ArithmeticException if numeric overflow occurs */ Temporal addTo(Temporal temporal); /** * Subtracts this object from the specified temporal object. * <p> * Subtracts the amount from the specified temporal object using the logic * encapsulated in the implementing class. * <p> * There are two equivalent ways of using this method. * The first is to invoke this method directly. * The second is to use {@link Temporal#minus(TemporalAmount)}: * <pre> * // these two lines are equivalent, but the second approach is recommended * dateTime = amount.subtractFrom(dateTime); * dateTime = dateTime.minus(amount); * </pre> * It is recommended to use the second approach, {@code minus(TemporalAmount)}, * as it is a lot clearer to read in code. * * @implSpec * The implementation must take the input object and subtract from it. * The implementation defines the logic of the subtraction and is responsible for * documenting that logic. It may use any method on {@code Temporal} to * query the temporal object and perform the subtraction. * The returned object must have the same observable type as the input object * <p> * The input object must not be altered. * Instead, an adjusted copy of the original must be returned. * This provides equivalent, safe behavior for immutable and mutable temporal objects. * <p> * The input temporal object may be in a calendar system other than ISO. * Implementations may choose to document compatibility with other calendar systems, * or reject non-ISO temporal objects by {@link TemporalQueries#chronology() querying the chronology}. * <p> * This method may be called from multiple threads in parallel. * It must be thread-safe when invoked. * * @param temporal the temporal object to subtract the amount from, not null * @return an object of the same observable type with the subtraction made, not null * @throws DateTimeException if unable to subtract * @throws ArithmeticException if numeric overflow occurs */ Temporal subtractFrom(Temporal temporal); }