* The rules model all the historic and future transitions for a time-zone. * {@link ZoneOffsetTransition} is used for known transitions, typically historic. * {@link ZoneOffsetTransitionRule} is used for future transitions that are based * on the result of an algorithm. *
* The same rules may be shared internally between multiple zone IDs. *
* Serializing an instance of {@code ZoneRules} will store the entire set of rules. * It does not store the zone ID as it is not part of the state of this object. *
* A rule implementation may or may not store full information about historic
* and future transitions, and the information stored is only as accurate as
* that supplied to the implementation by the rules provider.
* Applications should treat the data provided as representing the best information
* available to the implementation of this rule.
*
* @implSpec
* This class is immutable and thread-safe.
*
* @since 1.8
*/
public final class ZoneRules implements Serializable {
/**
* Serialization version.
*/
private static final long serialVersionUID = 3044319355680032515L;
/**
* The last year to have its transitions cached.
*/
private static final int LAST_CACHED_YEAR = 2100;
/**
* The transitions between standard offsets (epoch seconds), sorted.
*/
private final long[] standardTransitions;
/**
* The standard offsets.
*/
private final ZoneOffset[] standardOffsets;
/**
* The transitions between instants (epoch seconds), sorted.
*/
private final long[] savingsInstantTransitions;
/**
* The transitions between local date-times, sorted.
* This is a paired array, where the first entry is the start of the transition
* and the second entry is the end of the transition.
*/
private final LocalDateTime[] savingsLocalTransitions;
/**
* The wall offsets.
*/
private final ZoneOffset[] wallOffsets;
/**
* The last rule.
*/
private final ZoneOffsetTransitionRule[] lastRules;
/**
* The map of recent transitions.
*/
private final transient ConcurrentMap
* Epoch second values used for offsets are encoded in a variable
* length form to make the common cases put fewer bytes in the stream.
*
* ZoneOffset values are encoded in a variable length form so the
* common cases put fewer bytes in the stream.
*
* The mapping from an instant to an offset is simple, there is only
* one valid offset for each instant.
* This method returns that offset.
*
* @param instant the instant to find the offset for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the offset, not null
*/
public ZoneOffset getOffset(Instant instant) {
if (savingsInstantTransitions.length == 0) {
return standardOffsets[0];
}
long epochSec = instant.getEpochSecond();
// check if using last rules
if (lastRules.length > 0 &&
epochSec > savingsInstantTransitions[savingsInstantTransitions.length - 1]) {
int year = findYear(epochSec, wallOffsets[wallOffsets.length - 1]);
ZoneOffsetTransition[] transArray = findTransitionArray(year);
ZoneOffsetTransition trans = null;
for (int i = 0; i < transArray.length; i++) {
trans = transArray[i];
if (epochSec < trans.toEpochSecond()) {
return trans.getOffsetBefore();
}
}
return trans.getOffsetAfter();
}
// using historic rules
int index = Arrays.binarySearch(savingsInstantTransitions, epochSec);
if (index < 0) {
// switch negative insert position to start of matched range
index = -index - 2;
}
return wallOffsets[index + 1];
}
/**
* Gets a suitable offset for the specified local date-time in these rules.
*
* The mapping from a local date-time to an offset is not straightforward.
* There are three cases:
*
* Since, in the case of Gap and Overlap, the offset returned is a "best" value, rather
* than the "correct" value, it should be treated with care. Applications that care
* about the correct offset should use a combination of this method,
* {@link #getValidOffsets(LocalDateTime)} and {@link #getTransition(LocalDateTime)}.
*
* @param localDateTime the local date-time to query, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the best available offset for the local date-time, not null
*/
public ZoneOffset getOffset(LocalDateTime localDateTime) {
Object info = getOffsetInfo(localDateTime);
if (info instanceof ZoneOffsetTransition) {
return ((ZoneOffsetTransition) info).getOffsetBefore();
}
return (ZoneOffset) info;
}
/**
* Gets the offset applicable at the specified local date-time in these rules.
*
* The mapping from a local date-time to an offset is not straightforward.
* There are three cases:
*
* There are various ways to handle the conversion from a {@code LocalDateTime}.
* One technique, using this method, would be:
*
* In theory, it is possible for there to be more than two valid offsets.
* This would happen if clocks to be put back more than once in quick succession.
* This has never happened in the history of time-zones and thus has no special handling.
* However, if it were to happen, then the list would return more than 2 entries.
*
* @param localDateTime the local date-time to query for valid offsets, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the list of valid offsets, may be immutable, not null
*/
public List
* The mapping from a local date-time to an offset is not straightforward.
* There are three cases:
*
* There are various ways to handle the conversion from a {@code LocalDateTime}.
* One technique, using this method, would be:
*
* This provides access to historic information on how the standard offset
* has changed over time.
* The standard offset is the offset before any daylight saving time is applied.
* This is typically the offset applicable during winter.
*
* @param instant the instant to find the offset information for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the standard offset, not null
*/
public ZoneOffset getStandardOffset(Instant instant) {
if (savingsInstantTransitions.length == 0) {
return standardOffsets[0];
}
long epochSec = instant.getEpochSecond();
int index = Arrays.binarySearch(standardTransitions, epochSec);
if (index < 0) {
// switch negative insert position to start of matched range
index = -index - 2;
}
return standardOffsets[index + 1];
}
/**
* Gets the amount of daylight savings in use for the specified instant in this zone.
*
* This provides access to historic information on how the amount of daylight
* savings has changed over time.
* This is the difference between the standard offset and the actual offset.
* Typically the amount is zero during winter and one hour during summer.
* Time-zones are second-based, so the nanosecond part of the duration will be zero.
*
* This default implementation calculates the duration from the
* {@link #getOffset(java.time.Instant) actual} and
* {@link #getStandardOffset(java.time.Instant) standard} offsets.
*
* @param instant the instant to find the daylight savings for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the difference between the standard and actual offset, not null
*/
public Duration getDaylightSavings(Instant instant) {
if (savingsInstantTransitions.length == 0) {
return Duration.ZERO;
}
ZoneOffset standardOffset = getStandardOffset(instant);
ZoneOffset actualOffset = getOffset(instant);
return Duration.ofSeconds(actualOffset.getTotalSeconds() - standardOffset.getTotalSeconds());
}
/**
* Checks if the specified instant is in daylight savings.
*
* This checks if the standard offset and the actual offset are the same
* for the specified instant.
* If they are not, it is assumed that daylight savings is in operation.
*
* This default implementation compares the {@link #getOffset(java.time.Instant) actual}
* and {@link #getStandardOffset(java.time.Instant) standard} offsets.
*
* @param instant the instant to find the offset information for, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the standard offset, not null
*/
public boolean isDaylightSavings(Instant instant) {
return (getStandardOffset(instant).equals(getOffset(instant)) == false);
}
/**
* Checks if the offset date-time is valid for these rules.
*
* To be valid, the local date-time must not be in a gap and the offset
* must match one of the valid offsets.
*
* This default implementation checks if {@link #getValidOffsets(java.time.LocalDateTime)}
* contains the specified offset.
*
* @param localDateTime the date-time to check, not null, but null
* may be ignored if the rules have a single offset for all instants
* @param offset the offset to check, null returns false
* @return true if the offset date-time is valid for these rules
*/
public boolean isValidOffset(LocalDateTime localDateTime, ZoneOffset offset) {
return getValidOffsets(localDateTime).contains(offset);
}
/**
* Gets the next transition after the specified instant.
*
* This returns details of the next transition after the specified instant.
* For example, if the instant represents a point where "Summer" daylight savings time
* applies, then the method will return the transition to the next "Winter" time.
*
* @param instant the instant to get the next transition after, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the next transition after the specified instant, null if this is after the last transition
*/
public ZoneOffsetTransition nextTransition(Instant instant) {
if (savingsInstantTransitions.length == 0) {
return null;
}
long epochSec = instant.getEpochSecond();
// check if using last rules
if (epochSec >= savingsInstantTransitions[savingsInstantTransitions.length - 1]) {
if (lastRules.length == 0) {
return null;
}
// search year the instant is in
int year = findYear(epochSec, wallOffsets[wallOffsets.length - 1]);
ZoneOffsetTransition[] transArray = findTransitionArray(year);
for (ZoneOffsetTransition trans : transArray) {
if (epochSec < trans.toEpochSecond()) {
return trans;
}
}
// use first from following year
if (year < Year.MAX_VALUE) {
transArray = findTransitionArray(year + 1);
return transArray[0];
}
return null;
}
// using historic rules
int index = Arrays.binarySearch(savingsInstantTransitions, epochSec);
if (index < 0) {
index = -index - 1; // switched value is the next transition
} else {
index += 1; // exact match, so need to add one to get the next
}
return new ZoneOffsetTransition(savingsInstantTransitions[index], wallOffsets[index], wallOffsets[index + 1]);
}
/**
* Gets the previous transition before the specified instant.
*
* This returns details of the previous transition after the specified instant.
* For example, if the instant represents a point where "summer" daylight saving time
* applies, then the method will return the transition from the previous "winter" time.
*
* @param instant the instant to get the previous transition after, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the previous transition after the specified instant, null if this is before the first transition
*/
public ZoneOffsetTransition previousTransition(Instant instant) {
if (savingsInstantTransitions.length == 0) {
return null;
}
long epochSec = instant.getEpochSecond();
if (instant.getNano() > 0 && epochSec < Long.MAX_VALUE) {
epochSec += 1; // allow rest of method to only use seconds
}
// check if using last rules
long lastHistoric = savingsInstantTransitions[savingsInstantTransitions.length - 1];
if (lastRules.length > 0 && epochSec > lastHistoric) {
// search year the instant is in
ZoneOffset lastHistoricOffset = wallOffsets[wallOffsets.length - 1];
int year = findYear(epochSec, lastHistoricOffset);
ZoneOffsetTransition[] transArray = findTransitionArray(year);
for (int i = transArray.length - 1; i >= 0; i--) {
if (epochSec > transArray[i].toEpochSecond()) {
return transArray[i];
}
}
// use last from preceding year
int lastHistoricYear = findYear(lastHistoric, lastHistoricOffset);
if (--year > lastHistoricYear) {
transArray = findTransitionArray(year);
return transArray[transArray.length - 1];
}
// drop through
}
// using historic rules
int index = Arrays.binarySearch(savingsInstantTransitions, epochSec);
if (index < 0) {
index = -index - 1;
}
if (index <= 0) {
return null;
}
return new ZoneOffsetTransition(savingsInstantTransitions[index - 1], wallOffsets[index - 1], wallOffsets[index]);
}
private int findYear(long epochSecond, ZoneOffset offset) {
// inline for performance
long localSecond = epochSecond + offset.getTotalSeconds();
long localEpochDay = Math.floorDiv(localSecond, 86400);
return LocalDate.ofEpochDay(localEpochDay).getYear();
}
/**
* Gets the complete list of fully defined transitions.
*
* The complete set of transitions for this rules instance is defined by this method
* and {@link #getTransitionRules()}. This method returns those transitions that have
* been fully defined. These are typically historical, but may be in the future.
*
* The list will be empty for fixed offset rules and for any time-zone where there has
* only ever been a single offset. The list will also be empty if the transition rules are unknown.
*
* @return an immutable list of fully defined transitions, not null
*/
public List
* The complete set of transitions for this rules instance is defined by this method
* and {@link #getTransitions()}. This method returns instances of {@link ZoneOffsetTransitionRule}
* that define an algorithm for when transitions will occur.
*
* For any given {@code ZoneRules}, this list contains the transition rules for years
* beyond those years that have been fully defined. These rules typically refer to future
* daylight saving time rule changes.
*
* If the zone defines daylight savings into the future, then the list will normally
* be of size two and hold information about entering and exiting daylight savings.
* If the zone does not have daylight savings, or information about future changes
* is uncertain, then the list will be empty.
*
* The list will be empty for fixed offset rules and for any time-zone where there is no
* daylight saving time. The list will also be empty if the transition rules are unknown.
*
* @return an immutable list of transition rules, not null
*/
public List
* Two rule sets are equal if they will always result in the same output
* for any given input instant or local date-time.
* Rules from two different groups may return false even if they are in fact the same.
*
* This definition should result in implementations comparing their entire state.
*
* @param otherRules the other rules, null returns false
* @return true if this rules is the same as that specified
*/
@Override
public boolean equals(Object otherRules) {
if (this == otherRules) {
return true;
}
if (otherRules instanceof ZoneRules) {
ZoneRules other = (ZoneRules) otherRules;
return Arrays.equals(standardTransitions, other.standardTransitions) &&
Arrays.equals(standardOffsets, other.standardOffsets) &&
Arrays.equals(savingsInstantTransitions, other.savingsInstantTransitions) &&
Arrays.equals(wallOffsets, other.wallOffsets) &&
Arrays.equals(lastRules, other.lastRules);
}
return false;
}
/**
* Returns a suitable hash code given the definition of {@code #equals}.
*
* @return the hash code
*/
@Override
public int hashCode() {
return Arrays.hashCode(standardTransitions) ^
Arrays.hashCode(standardOffsets) ^
Arrays.hashCode(savingsInstantTransitions) ^
Arrays.hashCode(wallOffsets) ^
Arrays.hashCode(lastRules);
}
/**
* Returns a string describing this object.
*
* @return a string for debugging, not null
*/
@Override
public String toString() {
return "ZoneRules[currentStandardOffset=" + standardOffsets[standardOffsets.length - 1] + "]";
}
}
{@code
*
* out.writeByte(1); // identifies a ZoneRules
* out.writeInt(standardTransitions.length);
* for (long trans : standardTransitions) {
* Ser.writeEpochSec(trans, out);
* }
* for (ZoneOffset offset : standardOffsets) {
* Ser.writeOffset(offset, out);
* }
* out.writeInt(savingsInstantTransitions.length);
* for (long trans : savingsInstantTransitions) {
* Ser.writeEpochSec(trans, out);
* }
* for (ZoneOffset offset : wallOffsets) {
* Ser.writeOffset(offset, out);
* }
* out.writeByte(lastRules.length);
* for (ZoneOffsetTransitionRule rule : lastRules) {
* rule.writeExternal(out);
* }
* }
*
* {@code
*
* static void writeEpochSec(long epochSec, DataOutput out) throws IOException {
* if (epochSec >= -4575744000L && epochSec < 10413792000L && epochSec % 900 == 0) { // quarter hours between 1825 and 2300
* int store = (int) ((epochSec + 4575744000L) / 900);
* out.writeByte((store >>> 16) & 255);
* out.writeByte((store >>> 8) & 255);
* out.writeByte(store & 255);
* } else {
* out.writeByte(255);
* out.writeLong(epochSec);
* }
* }
* }
*
* {@code
*
* static void writeOffset(ZoneOffset offset, DataOutput out) throws IOException {
* final int offsetSecs = offset.getTotalSeconds();
* int offsetByte = offsetSecs % 900 == 0 ? offsetSecs / 900 : 127; // compress to -72 to +72
* out.writeByte(offsetByte);
* if (offsetByte == 127) {
* out.writeInt(offsetSecs);
* }
* }
*}
*
* @return the replacing object, not null
*/
private Object writeReplace() {
return new Ser(Ser.ZRULES, 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 {
out.writeInt(standardTransitions.length);
for (long trans : standardTransitions) {
Ser.writeEpochSec(trans, out);
}
for (ZoneOffset offset : standardOffsets) {
Ser.writeOffset(offset, out);
}
out.writeInt(savingsInstantTransitions.length);
for (long trans : savingsInstantTransitions) {
Ser.writeEpochSec(trans, out);
}
for (ZoneOffset offset : wallOffsets) {
Ser.writeOffset(offset, out);
}
out.writeByte(lastRules.length);
for (ZoneOffsetTransitionRule rule : lastRules) {
rule.writeExternal(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 ZoneRules readExternal(DataInput in) throws IOException, ClassNotFoundException {
int stdSize = in.readInt();
long[] stdTrans = (stdSize == 0) ? EMPTY_LONG_ARRAY
: new long[stdSize];
for (int i = 0; i < stdSize; i++) {
stdTrans[i] = Ser.readEpochSec(in);
}
ZoneOffset[] stdOffsets = new ZoneOffset[stdSize + 1];
for (int i = 0; i < stdOffsets.length; i++) {
stdOffsets[i] = Ser.readOffset(in);
}
int savSize = in.readInt();
long[] savTrans = (savSize == 0) ? EMPTY_LONG_ARRAY
: new long[savSize];
for (int i = 0; i < savSize; i++) {
savTrans[i] = Ser.readEpochSec(in);
}
ZoneOffset[] savOffsets = new ZoneOffset[savSize + 1];
for (int i = 0; i < savOffsets.length; i++) {
savOffsets[i] = Ser.readOffset(in);
}
int ruleSize = in.readByte();
ZoneOffsetTransitionRule[] rules = (ruleSize == 0) ?
EMPTY_LASTRULES : new ZoneOffsetTransitionRule[ruleSize];
for (int i = 0; i < ruleSize; i++) {
rules[i] = ZoneOffsetTransitionRule.readExternal(in);
}
return new ZoneRules(stdTrans, stdOffsets, savTrans, savOffsets, rules);
}
/**
* Checks of the zone rules are fixed, such that the offset never varies.
*
* @return true if the time-zone is fixed and the offset never changes
*/
public boolean isFixedOffset() {
return savingsInstantTransitions.length == 0;
}
/**
* Gets the offset applicable at the specified instant in these rules.
*
*
* Thus, for any given local date-time there can be zero, one or two valid offsets.
* This method returns the single offset in the Normal case, and in the Gap or Overlap
* case it returns the offset before the transition.
*
*
* Thus, for any given local date-time there can be zero, one or two valid offsets.
* This method returns that list of valid offsets, which is a list of size 0, 1 or 2.
* In the case where there are two offsets, the earlier offset is returned at index 0
* and the later offset at index 1.
*
* List<ZoneOffset> validOffsets = rules.getOffset(localDT);
* if (validOffsets.size() == 1) {
* // Normal case: only one valid offset
* zoneOffset = validOffsets.get(0);
* } else {
* // Gap or Overlap: determine what to do from transition (which will be non-null)
* ZoneOffsetTransition trans = rules.getTransition(localDT);
* }
*
*
*
* A transition is used to model the cases of a Gap or Overlap.
* The Normal case will return null.
*
* ZoneOffsetTransition trans = rules.getTransition(localDT);
* if (trans == null) {
* // Gap or Overlap: determine what to do from transition
* } else {
* // Normal case: only one valid offset
* zoneOffset = rule.getOffset(localDT);
* }
*
*
* @param localDateTime the local date-time to query for offset transition, not null, but null
* may be ignored if the rules have a single offset for all instants
* @return the offset transition, null if the local date-time is not in transition
*/
public ZoneOffsetTransition getTransition(LocalDateTime localDateTime) {
Object info = getOffsetInfo(localDateTime);
return (info instanceof ZoneOffsetTransition ? (ZoneOffsetTransition) info : null);
}
private Object getOffsetInfo(LocalDateTime dt) {
if (savingsInstantTransitions.length == 0) {
return standardOffsets[0];
}
// check if using last rules
if (lastRules.length > 0 &&
dt.isAfter(savingsLocalTransitions[savingsLocalTransitions.length - 1])) {
ZoneOffsetTransition[] transArray = findTransitionArray(dt.getYear());
Object info = null;
for (ZoneOffsetTransition trans : transArray) {
info = findOffsetInfo(dt, trans);
if (info instanceof ZoneOffsetTransition || info.equals(trans.getOffsetBefore())) {
return info;
}
}
return info;
}
// using historic rules
int index = Arrays.binarySearch(savingsLocalTransitions, dt);
if (index == -1) {
// before first transition
return wallOffsets[0];
}
if (index < 0) {
// switch negative insert position to start of matched range
index = -index - 2;
} else if (index < savingsLocalTransitions.length - 1 &&
savingsLocalTransitions[index].equals(savingsLocalTransitions[index + 1])) {
// handle overlap immediately following gap
index++;
}
if ((index & 1) == 0) {
// gap or overlap
LocalDateTime dtBefore = savingsLocalTransitions[index];
LocalDateTime dtAfter = savingsLocalTransitions[index + 1];
ZoneOffset offsetBefore = wallOffsets[index / 2];
ZoneOffset offsetAfter = wallOffsets[index / 2 + 1];
if (offsetAfter.getTotalSeconds() > offsetBefore.getTotalSeconds()) {
// gap
return new ZoneOffsetTransition(dtBefore, offsetBefore, offsetAfter);
} else {
// overlap
return new ZoneOffsetTransition(dtAfter, offsetBefore, offsetAfter);
}
} else {
// normal (neither gap or overlap)
return wallOffsets[index / 2 + 1];
}
}
/**
* Finds the offset info for a local date-time and transition.
*
* @param dt the date-time, not null
* @param trans the transition, not null
* @return the offset info, not null
*/
private Object findOffsetInfo(LocalDateTime dt, ZoneOffsetTransition trans) {
LocalDateTime localTransition = trans.getDateTimeBefore();
if (trans.isGap()) {
if (dt.isBefore(localTransition)) {
return trans.getOffsetBefore();
}
if (dt.isBefore(trans.getDateTimeAfter())) {
return trans;
} else {
return trans.getOffsetAfter();
}
} else {
if (dt.isBefore(localTransition) == false) {
return trans.getOffsetAfter();
}
if (dt.isBefore(trans.getDateTimeAfter())) {
return trans.getOffsetBefore();
} else {
return trans;
}
}
}
/**
* Finds the appropriate transition array for the given year.
*
* @param year the year, not null
* @return the transition array, not null
*/
private ZoneOffsetTransition[] findTransitionArray(int year) {
Integer yearObj = year; // should use Year class, but this saves a class load
ZoneOffsetTransition[] transArray = lastRulesCache.get(yearObj);
if (transArray != null) {
return transArray;
}
ZoneOffsetTransitionRule[] ruleArray = lastRules;
transArray = new ZoneOffsetTransition[ruleArray.length];
for (int i = 0; i < ruleArray.length; i++) {
transArray[i] = ruleArray[i].createTransition(year);
}
if (year < LAST_CACHED_YEAR) {
lastRulesCache.putIfAbsent(yearObj, transArray);
}
return transArray;
}
/**
* Gets the standard offset for the specified instant in this zone.
*