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/*
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* Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
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* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright notice,
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package java.time.zone;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.time.Duration;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
/**
* A transition between two offsets caused by a discontinuity in the local time-line.
* <p>
* A transition between two offsets is normally the result of a daylight savings cutover.
* The discontinuity is normally a gap in spring and an overlap in autumn.
* {@code ZoneOffsetTransition} models the transition between the two offsets.
* <p>
* Gaps occur where there are local date-times that simply do not not exist.
* An example would be when the offset changes from {@code +03:00} to {@code +04:00}.
* This might be described as 'the clocks will move forward one hour tonight at 1am'.
* <p>
* Overlaps occur where there are local date-times that exist twice.
* An example would be when the offset changes from {@code +04:00} to {@code +03:00}.
* This might be described as 'the clocks will move back one hour tonight at 2am'.
*
* @implSpec
* This class is immutable and thread-safe.
*
* @since 1.8
*/
public final class ZoneOffsetTransition
implements Comparable<ZoneOffsetTransition>, Serializable {
/**
* Serialization version.
*/
private static final long serialVersionUID = -6946044323557704546L;
/**
* The local transition date-time at the transition.
*/
private final LocalDateTime transition;
/**
* The offset before transition.
*/
private final ZoneOffset offsetBefore;
/**
* The offset after transition.
*/
private final ZoneOffset offsetAfter;
//-----------------------------------------------------------------------
/**
* Obtains an instance defining a transition between two offsets.
* <p>
* Applications should normally obtain an instance from {@link ZoneRules}.
* This factory is only intended for use when creating {@link ZoneRules}.
*
* @param transition the transition date-time at the transition, which never
* actually occurs, expressed local to the before offset, not null
* @param offsetBefore the offset before the transition, not null
* @param offsetAfter the offset at and after the transition, not null
* @return the transition, not null
* @throws IllegalArgumentException if {@code offsetBefore} and {@code offsetAfter}
* are equal, or {@code transition.getNano()} returns non-zero value
*/
public static ZoneOffsetTransition of(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
Objects.requireNonNull(transition, "transition");
Objects.requireNonNull(offsetBefore, "offsetBefore");
Objects.requireNonNull(offsetAfter, "offsetAfter");
if (offsetBefore.equals(offsetAfter)) {
throw new IllegalArgumentException("Offsets must not be equal");
}
if (transition.getNano() != 0) {
throw new IllegalArgumentException("Nano-of-second must be zero");
}
return new ZoneOffsetTransition(transition, offsetBefore, offsetAfter);
}
/**
* Creates an instance defining a transition between two offsets.
*
* @param transition the transition date-time with the offset before the transition, not null
* @param offsetBefore the offset before the transition, not null
* @param offsetAfter the offset at and after the transition, not null
*/
ZoneOffsetTransition(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
this.transition = transition;
this.offsetBefore = offsetBefore;
this.offsetAfter = offsetAfter;
}
/**
* Creates an instance from epoch-second and offsets.
*
* @param epochSecond the transition epoch-second
* @param offsetBefore the offset before the transition, not null
* @param offsetAfter the offset at and after the transition, not null
*/
ZoneOffsetTransition(long epochSecond, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
this.transition = LocalDateTime.ofEpochSecond(epochSecond, 0, offsetBefore);
this.offsetBefore = offsetBefore;
this.offsetAfter = offsetAfter;
}
//-----------------------------------------------------------------------
/**
* Defend against malicious streams.
*
* @param s the stream to read
* @throws InvalidObjectException always
*/
private void readObject(ObjectInputStream s) throws InvalidObjectException {
throw new InvalidObjectException("Deserialization via serialization delegate");
}
/**
* Writes the object using a
* <a href="../../../serialized-form.html#java.time.zone.Ser">dedicated serialized form</a>.
* @serialData
* Refer to the serialized form of
* <a href="../../../serialized-form.html#java.time.zone.ZoneRules">ZoneRules.writeReplace</a>
* for the encoding of epoch seconds and offsets.
* <pre style="font-size:1.0em">{@code
*
* out.writeByte(2); // identifies a ZoneOffsetTransition
* out.writeEpochSec(toEpochSecond);
* out.writeOffset(offsetBefore);
* out.writeOffset(offsetAfter);
* }
* </pre>
* @return the replacing object, not null
*/
private Object writeReplace() {
return new Ser(Ser.ZOT, this);
}
/**
* Writes the state to the stream.
*
* @param out the output stream, not null
* @throws IOException if an error occurs
*/
void writeExternal(DataOutput out) throws IOException {
Ser.writeEpochSec(toEpochSecond(), out);
Ser.writeOffset(offsetBefore, out);
Ser.writeOffset(offsetAfter, out);
}
/**
* Reads the state from the stream.
*
* @param in the input stream, not null
* @return the created object, not null
* @throws IOException if an error occurs
*/
static ZoneOffsetTransition readExternal(DataInput in) throws IOException {
long epochSecond = Ser.readEpochSec(in);
ZoneOffset before = Ser.readOffset(in);
ZoneOffset after = Ser.readOffset(in);
if (before.equals(after)) {
throw new IllegalArgumentException("Offsets must not be equal");
}
return new ZoneOffsetTransition(epochSecond, before, after);
}
//-----------------------------------------------------------------------
/**
* Gets the transition instant.
* <p>
* This is the instant of the discontinuity, which is defined as the first
* instant that the 'after' offset applies.
* <p>
* The methods {@link #getInstant()}, {@link #getDateTimeBefore()} and {@link #getDateTimeAfter()}
* all represent the same instant.
*
* @return the transition instant, not null
*/
public Instant getInstant() {
return transition.toInstant(offsetBefore);
}
/**
* Gets the transition instant as an epoch second.
*
* @return the transition epoch second
*/
public long toEpochSecond() {
return transition.toEpochSecond(offsetBefore);
}
//-------------------------------------------------------------------------
/**
* Gets the local transition date-time, as would be expressed with the 'before' offset.
* <p>
* This is the date-time where the discontinuity begins expressed with the 'before' offset.
* At this instant, the 'after' offset is actually used, therefore the combination of this
* date-time and the 'before' offset will never occur.
* <p>
* The combination of the 'before' date-time and offset represents the same instant
* as the 'after' date-time and offset.
*
* @return the transition date-time expressed with the before offset, not null
*/
public LocalDateTime getDateTimeBefore() {
return transition;
}
/**
* Gets the local transition date-time, as would be expressed with the 'after' offset.
* <p>
* This is the first date-time after the discontinuity, when the new offset applies.
* <p>
* The combination of the 'before' date-time and offset represents the same instant
* as the 'after' date-time and offset.
*
* @return the transition date-time expressed with the after offset, not null
*/
public LocalDateTime getDateTimeAfter() {
return transition.plusSeconds(getDurationSeconds());
}
/**
* Gets the offset before the transition.
* <p>
* This is the offset in use before the instant of the transition.
*
* @return the offset before the transition, not null
*/
public ZoneOffset getOffsetBefore() {
return offsetBefore;
}
/**
* Gets the offset after the transition.
* <p>
* This is the offset in use on and after the instant of the transition.
*
* @return the offset after the transition, not null
*/
public ZoneOffset getOffsetAfter() {
return offsetAfter;
}
/**
* Gets the duration of the transition.
* <p>
* In most cases, the transition duration is one hour, however this is not always the case.
* The duration will be positive for a gap and negative for an overlap.
* Time-zones are second-based, so the nanosecond part of the duration will be zero.
*
* @return the duration of the transition, positive for gaps, negative for overlaps
*/
public Duration getDuration() {
return Duration.ofSeconds(getDurationSeconds());
}
/**
* Gets the duration of the transition in seconds.
*
* @return the duration in seconds
*/
private int getDurationSeconds() {
return getOffsetAfter().getTotalSeconds() - getOffsetBefore().getTotalSeconds();
}
/**
* Does this transition represent a gap in the local time-line.
* <p>
* Gaps occur where there are local date-times that simply do not not exist.
* An example would be when the offset changes from {@code +01:00} to {@code +02:00}.
* This might be described as 'the clocks will move forward one hour tonight at 1am'.
*
* @return true if this transition is a gap, false if it is an overlap
*/
public boolean isGap() {
return getOffsetAfter().getTotalSeconds() > getOffsetBefore().getTotalSeconds();
}
/**
* Does this transition represent an overlap in the local time-line.
* <p>
* Overlaps occur where there are local date-times that exist twice.
* An example would be when the offset changes from {@code +02:00} to {@code +01:00}.
* This might be described as 'the clocks will move back one hour tonight at 2am'.
*
* @return true if this transition is an overlap, false if it is a gap
*/
public boolean isOverlap() {
return getOffsetAfter().getTotalSeconds() < getOffsetBefore().getTotalSeconds();
}
/**
* Checks if the specified offset is valid during this transition.
* <p>
* This checks to see if the given offset will be valid at some point in the transition.
* A gap will always return false.
* An overlap will return true if the offset is either the before or after offset.
*
* @param offset the offset to check, null returns false
* @return true if the offset is valid during the transition
*/
public boolean isValidOffset(ZoneOffset offset) {
return isGap() ? false : (getOffsetBefore().equals(offset) || getOffsetAfter().equals(offset));
}
/**
* Gets the valid offsets during this transition.
* <p>
* A gap will return an empty list, while an overlap will return both offsets.
*
* @return the list of valid offsets
*/
List<ZoneOffset> getValidOffsets() {
if (isGap()) {
return Collections.emptyList();
}
return Arrays.asList(getOffsetBefore(), getOffsetAfter());
}
//-----------------------------------------------------------------------
/**
* Compares this transition to another based on the transition instant.
* <p>
* This compares the instants of each transition.
* The offsets are ignored, making this order inconsistent with equals.
*
* @param transition the transition to compare to, not null
* @return the comparator value, negative if less, positive if greater
*/
@Override
public int compareTo(ZoneOffsetTransition transition) {
return this.getInstant().compareTo(transition.getInstant());
}
//-----------------------------------------------------------------------
/**
* Checks if this object equals another.
* <p>
* The entire state of the object is compared.
*
* @param other the other object to compare to, null returns false
* @return true if equal
*/
@Override
public boolean equals(Object other) {
if (other == this) {
return true;
}
if (other instanceof ZoneOffsetTransition) {
ZoneOffsetTransition d = (ZoneOffsetTransition) other;
return transition.equals(d.transition) &&
offsetBefore.equals(d.offsetBefore) && offsetAfter.equals(d.offsetAfter);
}
return false;
}
/**
* Returns a suitable hash code.
*
* @return the hash code
*/
@Override
public int hashCode() {
return transition.hashCode() ^ offsetBefore.hashCode() ^ Integer.rotateLeft(offsetAfter.hashCode(), 16);
}
//-----------------------------------------------------------------------
/**
* Returns a string describing this object.
*
* @return a string for debugging, not null
*/
@Override
public String toString() {
StringBuilder buf = new StringBuilder();
buf.append("Transition[")
.append(isGap() ? "Gap" : "Overlap")
.append(" at ")
.append(transition)
.append(offsetBefore)
.append(" to ")
.append(offsetAfter)
.append(']');
return buf.toString();
}
}