461 lines
17 KiB
Java
461 lines
17 KiB
Java
/*
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* Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* * Neither the name of JSR-310 nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package java.time.zone;
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import java.io.DataInput;
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import java.io.DataOutput;
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import java.io.IOException;
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import java.io.InvalidObjectException;
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import java.io.ObjectInputStream;
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import java.io.Serializable;
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import java.time.Duration;
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import java.time.Instant;
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import java.time.LocalDateTime;
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import java.time.ZoneOffset;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.List;
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import java.util.Objects;
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/**
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* A transition between two offsets caused by a discontinuity in the local time-line.
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* <p>
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* A transition between two offsets is normally the result of a daylight savings cutover.
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* The discontinuity is normally a gap in spring and an overlap in autumn.
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* {@code ZoneOffsetTransition} models the transition between the two offsets.
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* <p>
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* Gaps occur where there are local date-times that simply do not exist.
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* An example would be when the offset changes from {@code +03:00} to {@code +04:00}.
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* This might be described as 'the clocks will move forward one hour tonight at 1am'.
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* <p>
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* Overlaps occur where there are local date-times that exist twice.
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* An example would be when the offset changes from {@code +04:00} to {@code +03:00}.
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* This might be described as 'the clocks will move back one hour tonight at 2am'.
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*
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* @implSpec
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* This class is immutable and thread-safe.
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*
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* @since 1.8
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*/
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public final class ZoneOffsetTransition
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implements Comparable<ZoneOffsetTransition>, Serializable {
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/**
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* Serialization version.
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*/
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private static final long serialVersionUID = -6946044323557704546L;
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/**
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* The transition epoch-second.
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*/
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private final long epochSecond;
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/**
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* The local transition date-time at the transition.
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*/
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private final LocalDateTime transition;
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/**
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* The offset before transition.
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*/
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private final ZoneOffset offsetBefore;
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/**
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* The offset after transition.
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*/
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private final ZoneOffset offsetAfter;
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//-----------------------------------------------------------------------
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/**
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* Obtains an instance defining a transition between two offsets.
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* <p>
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* Applications should normally obtain an instance from {@link ZoneRules}.
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* This factory is only intended for use when creating {@link ZoneRules}.
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*
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* @param transition the transition date-time at the transition, which never
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* actually occurs, expressed local to the before offset, not null
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* @param offsetBefore the offset before the transition, not null
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* @param offsetAfter the offset at and after the transition, not null
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* @return the transition, not null
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* @throws IllegalArgumentException if {@code offsetBefore} and {@code offsetAfter}
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* are equal, or {@code transition.getNano()} returns non-zero value
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*/
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public static ZoneOffsetTransition of(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
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Objects.requireNonNull(transition, "transition");
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Objects.requireNonNull(offsetBefore, "offsetBefore");
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Objects.requireNonNull(offsetAfter, "offsetAfter");
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if (offsetBefore.equals(offsetAfter)) {
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throw new IllegalArgumentException("Offsets must not be equal");
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}
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if (transition.getNano() != 0) {
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throw new IllegalArgumentException("Nano-of-second must be zero");
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}
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return new ZoneOffsetTransition(transition, offsetBefore, offsetAfter);
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}
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/**
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* Creates an instance defining a transition between two offsets.
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*
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* @param transition the transition date-time with the offset before the transition, not null
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* @param offsetBefore the offset before the transition, not null
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* @param offsetAfter the offset at and after the transition, not null
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*/
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ZoneOffsetTransition(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
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assert transition.getNano() == 0;
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this.epochSecond = transition.toEpochSecond(offsetBefore);
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this.transition = transition;
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this.offsetBefore = offsetBefore;
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this.offsetAfter = offsetAfter;
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}
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/**
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* Creates an instance from epoch-second and offsets.
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*
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* @param epochSecond the transition epoch-second
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* @param offsetBefore the offset before the transition, not null
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* @param offsetAfter the offset at and after the transition, not null
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*/
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ZoneOffsetTransition(long epochSecond, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
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this.epochSecond = epochSecond;
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this.transition = LocalDateTime.ofEpochSecond(epochSecond, 0, offsetBefore);
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this.offsetBefore = offsetBefore;
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this.offsetAfter = offsetAfter;
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}
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//-----------------------------------------------------------------------
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/**
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* Defend against malicious streams.
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*
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* @param s the stream to read
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* @throws InvalidObjectException always
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*/
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private void readObject(ObjectInputStream s) throws InvalidObjectException {
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throw new InvalidObjectException("Deserialization via serialization delegate");
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}
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/**
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* Writes the object using a
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* <a href="{@docRoot}/serialized-form.html#java.time.zone.Ser">dedicated serialized form</a>.
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* @serialData
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* Refer to the serialized form of
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* <a href="{@docRoot}/serialized-form.html#java.time.zone.ZoneRules">ZoneRules.writeReplace</a>
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* for the encoding of epoch seconds and offsets.
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* <pre style="font-size:1.0em">{@code
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*
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* out.writeByte(2); // identifies a ZoneOffsetTransition
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* out.writeEpochSec(toEpochSecond);
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* out.writeOffset(offsetBefore);
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* out.writeOffset(offsetAfter);
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* }
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* </pre>
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* @return the replacing object, not null
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*/
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private Object writeReplace() {
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return new Ser(Ser.ZOT, this);
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}
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/**
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* Writes the state to the stream.
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*
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* @param out the output stream, not null
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* @throws IOException if an error occurs
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*/
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void writeExternal(DataOutput out) throws IOException {
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Ser.writeEpochSec(epochSecond, out);
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Ser.writeOffset(offsetBefore, out);
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Ser.writeOffset(offsetAfter, out);
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}
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/**
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* Reads the state from the stream.
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*
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* @param in the input stream, not null
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* @return the created object, not null
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* @throws IOException if an error occurs
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*/
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static ZoneOffsetTransition readExternal(DataInput in) throws IOException {
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long epochSecond = Ser.readEpochSec(in);
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ZoneOffset before = Ser.readOffset(in);
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ZoneOffset after = Ser.readOffset(in);
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if (before.equals(after)) {
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throw new IllegalArgumentException("Offsets must not be equal");
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}
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return new ZoneOffsetTransition(epochSecond, before, after);
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}
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//-----------------------------------------------------------------------
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/**
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* Gets the transition instant.
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* <p>
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* This is the instant of the discontinuity, which is defined as the first
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* instant that the 'after' offset applies.
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* <p>
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* The methods {@link #getInstant()}, {@link #getDateTimeBefore()} and {@link #getDateTimeAfter()}
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* all represent the same instant.
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*
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* @return the transition instant, not null
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*/
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public Instant getInstant() {
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return Instant.ofEpochSecond(epochSecond);
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}
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/**
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* Gets the transition instant as an epoch second.
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*
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* @return the transition epoch second
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*/
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public long toEpochSecond() {
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return epochSecond;
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}
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//-------------------------------------------------------------------------
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/**
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* Gets the local transition date-time, as would be expressed with the 'before' offset.
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* <p>
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* This is the date-time where the discontinuity begins expressed with the 'before' offset.
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* At this instant, the 'after' offset is actually used, therefore the combination of this
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* date-time and the 'before' offset will never occur.
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* <p>
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* The combination of the 'before' date-time and offset represents the same instant
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* as the 'after' date-time and offset.
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*
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* @return the transition date-time expressed with the before offset, not null
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*/
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public LocalDateTime getDateTimeBefore() {
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return transition;
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}
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/**
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* Gets the local transition date-time, as would be expressed with the 'after' offset.
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* <p>
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* This is the first date-time after the discontinuity, when the new offset applies.
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* <p>
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* The combination of the 'before' date-time and offset represents the same instant
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* as the 'after' date-time and offset.
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*
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* @return the transition date-time expressed with the after offset, not null
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*/
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public LocalDateTime getDateTimeAfter() {
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return transition.plusSeconds(getDurationSeconds());
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}
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/**
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* Gets the offset before the transition.
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* <p>
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* This is the offset in use before the instant of the transition.
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*
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* @return the offset before the transition, not null
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*/
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public ZoneOffset getOffsetBefore() {
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return offsetBefore;
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}
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/**
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* Gets the offset after the transition.
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* <p>
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* This is the offset in use on and after the instant of the transition.
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*
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* @return the offset after the transition, not null
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*/
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public ZoneOffset getOffsetAfter() {
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return offsetAfter;
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}
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/**
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* Gets the duration of the transition.
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* <p>
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* In most cases, the transition duration is one hour, however this is not always the case.
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* The duration will be positive for a gap and negative for an overlap.
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* Time-zones are second-based, so the nanosecond part of the duration will be zero.
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*
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* @return the duration of the transition, positive for gaps, negative for overlaps
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*/
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public Duration getDuration() {
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return Duration.ofSeconds(getDurationSeconds());
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}
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/**
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* Gets the duration of the transition in seconds.
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*
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* @return the duration in seconds
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*/
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private int getDurationSeconds() {
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return getOffsetAfter().getTotalSeconds() - getOffsetBefore().getTotalSeconds();
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}
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/**
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* Does this transition represent a gap in the local time-line.
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* <p>
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* Gaps occur where there are local date-times that simply do not exist.
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* An example would be when the offset changes from {@code +01:00} to {@code +02:00}.
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* This might be described as 'the clocks will move forward one hour tonight at 1am'.
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*
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* @return true if this transition is a gap, false if it is an overlap
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*/
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public boolean isGap() {
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return getOffsetAfter().getTotalSeconds() > getOffsetBefore().getTotalSeconds();
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}
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/**
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* Does this transition represent an overlap in the local time-line.
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* <p>
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* Overlaps occur where there are local date-times that exist twice.
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* An example would be when the offset changes from {@code +02:00} to {@code +01:00}.
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* This might be described as 'the clocks will move back one hour tonight at 2am'.
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*
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* @return true if this transition is an overlap, false if it is a gap
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*/
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public boolean isOverlap() {
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return getOffsetAfter().getTotalSeconds() < getOffsetBefore().getTotalSeconds();
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}
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/**
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* Checks if the specified offset is valid during this transition.
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* <p>
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* This checks to see if the given offset will be valid at some point in the transition.
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* A gap will always return false.
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* An overlap will return true if the offset is either the before or after offset.
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*
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* @param offset the offset to check, null returns false
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* @return true if the offset is valid during the transition
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*/
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public boolean isValidOffset(ZoneOffset offset) {
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return isGap() ? false : (getOffsetBefore().equals(offset) || getOffsetAfter().equals(offset));
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}
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/**
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* Gets the valid offsets during this transition.
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* <p>
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* A gap will return an empty list, while an overlap will return both offsets.
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*
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* @return the list of valid offsets
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*/
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List<ZoneOffset> getValidOffsets() {
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if (isGap()) {
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return List.of();
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}
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return List.of(getOffsetBefore(), getOffsetAfter());
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}
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//-----------------------------------------------------------------------
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/**
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* Compares this transition to another based on the transition instant.
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* <p>
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* This compares the instants of each transition.
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* The offsets are ignored, making this order inconsistent with equals.
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*
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* @param transition the transition to compare to, not null
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* @return the comparator value, negative if less, positive if greater
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*/
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@Override
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public int compareTo(ZoneOffsetTransition transition) {
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return Long.compare(epochSecond, transition.epochSecond);
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}
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//-----------------------------------------------------------------------
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/**
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* Checks if this object equals another.
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* <p>
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* The entire state of the object is compared.
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*
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* @param other the other object to compare to, null returns false
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* @return true if equal
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*/
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@Override
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public boolean equals(Object other) {
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if (other == this) {
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return true;
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}
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return (other instanceof ZoneOffsetTransition d)
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&& epochSecond == d.epochSecond
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&& offsetBefore.equals(d.offsetBefore)
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&& offsetAfter.equals(d.offsetAfter);
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}
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/**
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* Returns a suitable hash code.
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*
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* @return the hash code
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*/
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@Override
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public int hashCode() {
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return transition.hashCode() ^ offsetBefore.hashCode() ^ Integer.rotateLeft(offsetAfter.hashCode(), 16);
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}
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//-----------------------------------------------------------------------
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/**
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* Returns a string describing this object.
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*
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* @return a string for debugging, not null
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*/
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@Override
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public String toString() {
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StringBuilder buf = new StringBuilder();
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buf.append("Transition[")
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.append(isGap() ? "Gap" : "Overlap")
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.append(" at ")
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.append(transition)
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.append(offsetBefore)
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.append(" to ")
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.append(offsetAfter)
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.append(']');
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return buf.toString();
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}
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}
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