Don't throw IllegalInstantException to determine DST gap
By taking the logic from DateTimeZone#convertLocalToUTC(long, boolean) we can avoid throwing the exception.
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@ -219,19 +219,56 @@ public abstract class TimeZoneRounding extends Rounding {
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public long roundKey(long utcMillis) {
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long timeLocal = timeZone.convertUTCToLocal(utcMillis);
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long rounded = Rounding.Interval.roundValue(Rounding.Interval.roundKey(timeLocal, interval), interval);
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try {
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return timeZone.convertLocalToUTC(rounded, true, utcMillis);
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} catch (IllegalInstantException e) {
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long roundedUTC;
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if (isInDSTGap(rounded) == false) {
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roundedUTC = timeZone.convertLocalToUTC(rounded, true, utcMillis);
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} else {
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/*
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* The rounded local time is illegal and landed in a DST gap. In
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* this case, we choose 1ms tick after the transition date. We
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* don't want the transition date itself because those dates,
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* when rounded themselves, fall into the previous interval.
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* This would violate the invariant that the rounding operation
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* should be idempotent.
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* Edge case where the rounded local time is illegal and landed
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* in a DST gap. In this case, we choose 1ms tick after the
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* transition date. We don't want the transition date itself
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* because those dates, when rounded themselves, fall into the
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* previous interval. This would violate the invariant that the
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* rounding operation should be idempotent.
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*/
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return timeZone.previousTransition(utcMillis) + 1;
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roundedUTC = timeZone.previousTransition(utcMillis) + 1;
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}
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return roundedUTC;
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}
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/**
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* Determine whether the local instant is a valid instant in the given
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* time zone. The logic for this is taken from
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* {@link DateTimeZone#convertLocalToUTC(long, boolean)} for the
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* `strict` mode case, but instead of throwing an
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* {@link IllegalInstantException}, which is costly, we want to return a
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* flag indicating that the value is illegal in that time zone.
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*/
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private boolean isInDSTGap(long instantLocal) {
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if (timeZone.isFixed()) {
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return false;
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}
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// get the offset at instantLocal (first estimate)
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int offsetLocal = timeZone.getOffset(instantLocal);
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// adjust instantLocal using the estimate and recalc the offset
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int offset = timeZone.getOffset(instantLocal - offsetLocal);
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// if the offsets differ, we must be near a DST boundary
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if (offsetLocal != offset) {
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// determine if we are in the DST gap
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long nextLocal = timeZone.nextTransition(instantLocal - offsetLocal);
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if (nextLocal == (instantLocal - offsetLocal)) {
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nextLocal = Long.MAX_VALUE;
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}
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long nextAdjusted = timeZone.nextTransition(instantLocal - offset);
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if (nextAdjusted == (instantLocal - offset)) {
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nextAdjusted = Long.MAX_VALUE;
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}
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if (nextLocal != nextAdjusted) {
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// we are in the DST gap
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return true;
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}
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}
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return false;
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}
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@Override
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