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6936350: API clarification needed on useDaylightTime() for timezones that have defined usage dates

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Reviewed-by: peytoia
This commit is contained in:
Masayoshi Okutsu 2011-02-16 16:51:21 +09:00
parent a2309c8fe0
commit 0bfde7d243
3 changed files with 179 additions and 27 deletions
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21
jdk/src/share/classes/java/util/SimpleTimeZone.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1996, 2011, 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
@ -825,10 +825,7 @@ public class SimpleTimeZone extends TimeZone {
* @since 1.2
*/
public int getDSTSavings() {
if (useDaylight) {
return dstSavings;
}
return 0;
return useDaylight ? dstSavings : 0;
}
/**
@ -841,6 +838,20 @@ public class SimpleTimeZone extends TimeZone {
return useDaylight;
}
/**
* Returns {@code true} if this {@code SimpleTimeZone} observes
* Daylight Saving Time. This method is equivalent to {@link
* #useDaylightTime()}.
*
* @return {@code true} if this {@code SimpleTimeZone} observes
* Daylight Saving Time; {@code false} otherwise.
* @since 1.7
*/
@Override
public boolean observesDaylightTime() {
return useDaylightTime();
}
/**
* Queries if the given date is in daylight saving time.
* @return true if daylight saving time is in effective at the

82
jdk/src/share/classes/java/util/TimeZone.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1996, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1996, 2011, 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
@ -455,17 +455,28 @@ abstract public class TimeZone implements Serializable, Cloneable {
/**
* Returns the amount of time to be added to local standard time
* to get local wall clock time.
* <p>
* The default implementation always returns 3600000 milliseconds
* (i.e., one hour) if this time zone observes Daylight Saving
* Time. Otherwise, 0 (zero) is returned.
* <p>
* If an underlying TimeZone implementation subclass supports
* historical Daylight Saving Time changes, this method returns
* the known latest daylight saving value.
*
* <p>The default implementation returns 3600000 milliseconds
* (i.e., one hour) if a call to {@link #useDaylightTime()}
* returns {@code true}. Otherwise, 0 (zero) is returned.
*
* <p>If an underlying {@code TimeZone} implementation subclass
* supports historical and future Daylight Saving Time schedule
* changes, this method returns the amount of saving time of the
* last known Daylight Saving Time rule that can be a future
* prediction.
*
* <p>If the amount of saving time at any given time stamp is
* required, construct a {@link Calendar} with this {@code
* TimeZone} and the time stamp, and call {@link Calendar#get(int)
* Calendar.get}{@code (}{@link Calendar#DST_OFFSET}{@code )}.
*
* @return the amount of saving time in milliseconds
* @since 1.4
* @see #inDaylightTime(Date)
* @see #getOffset(long)
* @see #getOffset(int,int,int,int,int,int)
* @see Calendar#ZONE_OFFSET
*/
public int getDSTSavings() {
if (useDaylightTime()) {
@ -475,24 +486,51 @@ abstract public class TimeZone implements Serializable, Cloneable {
}
/**
* Queries if this time zone uses daylight savings time.
* <p>
* If an underlying <code>TimeZone</code> implementation subclass
* supports historical Daylight Saving Time schedule changes, the
* method refers to the latest Daylight Saving Time schedule
* information.
* Queries if this {@code TimeZone} uses Daylight Saving Time.
*
* @return true if this time zone uses daylight savings time,
* false, otherwise.
* <p>If an underlying {@code TimeZone} implementation subclass
* supports historical and future Daylight Saving Time schedule
* changes, this method refers to the last known Daylight Saving Time
* rule that can be a future prediction and may not be the same as
* the current rule. Consider calling {@link #observesDaylightTime()}
* if the current rule should also be taken into account.
*
* @return {@code true} if this {@code TimeZone} uses Daylight Saving Time,
* {@code false}, otherwise.
* @see #inDaylightTime(Date)
* @see Calendar#DST_OFFSET
*/
public abstract boolean useDaylightTime();
/**
* Queries if the given date is in daylight savings time in
* this time zone.
* @param date the given Date.
* @return true if the given date is in daylight savings time,
* false, otherwise.
* Returns {@code true} if this {@code TimeZone} is currently in
* Daylight Saving Time, or if a transition from Standard Time to
* Daylight Saving Time occurs at any future time.
*
* <p>The default implementation returns {@code true} if
* {@code useDaylightTime()} or {@code inDaylightTime(new Date())}
* returns {@code true}.
*
* @return {@code true} if this {@code TimeZone} is currently in
* Daylight Saving Time, or if a transition from Standard Time to
* Daylight Saving Time occurs at any future time; {@code false}
* otherwise.
* @since 1.7
* @see #useDaylightTime()
* @see #inDaylightTime(Date)
* @see Calendar#DST_OFFSET
*/
public boolean observesDaylightTime() {
return useDaylightTime() || inDaylightTime(new Date());
}
/**
* Queries if the given {@code date} is in Daylight Saving Time in
* this {@code TimeZone}.
*
* @param date the given {@code Date}.
* @return {@code true} if the given {@code date} is in Daylight Saving Time,
* {@code false}, otherwise.
*/
abstract public boolean inDaylightTime(Date date);

103
jdk/test/java/util/TimeZone/DaylightTimeTest.java Normal file
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@ -0,0 +1,103 @@
/*
* Copyright (c) 2011, 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.
*
* 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.
*/
/*
* @test
* @bug 6936350
* @summary Test case for TimeZone.observesDaylightTime()
*/
import java.util.*;
import static java.util.GregorianCalendar.*;
public class DaylightTimeTest {
private static final int ONE_HOUR = 60 * 60 * 1000; // one hour
private static final int INTERVAL = 24 * ONE_HOUR; // one day
private static final String[] ZONES = TimeZone.getAvailableIDs();
private static int errors = 0;
public static void main(String[] args) {
// Test default TimeZone
for (String id : ZONES) {
TimeZone tz = TimeZone.getTimeZone(id);
long now = System.currentTimeMillis();
boolean observes = tz.observesDaylightTime();
boolean found = findDSTTransition(tz, now);
if (observes != found) {
// There's a critical section. If DST ends after the
// System.currentTimeMills() call, there should be
// inconsistency in the determination. Try the same
// thing again to see the inconsistency was due to the
// critical section.
now = System.currentTimeMillis();
observes = tz.observesDaylightTime();
found = findDSTTransition(tz, now);
if (observes != found) {
System.err.printf("%s: observesDaylightTime() should return %s at %d%n",
tz.getID(), found, now);
errors++;
}
}
}
// Test SimpleTimeZone in which observesDaylightTime() is
// equivalent to useDaylightTime().
testSimpleTimeZone(new SimpleTimeZone(-8*ONE_HOUR, "X",
APRIL, 1, -SUNDAY, 2*ONE_HOUR,
OCTOBER, -1, SUNDAY, 2*ONE_HOUR,
1*ONE_HOUR));
testSimpleTimeZone(new SimpleTimeZone(-8*ONE_HOUR, "Y"));
if (errors > 0) {
throw new RuntimeException("DaylightTimeTest: failed");
}
}
/**
* Returns true if it's `now' in DST or there's any
* standard-to-daylight transition within 50 years after `now'.
*/
private static boolean findDSTTransition(TimeZone tz, long now) {
GregorianCalendar cal = new GregorianCalendar(tz, Locale.US);
cal.setTimeInMillis(now);
cal.add(YEAR, 50);
long end = cal.getTimeInMillis();
for (long t = now; t < end; t += INTERVAL) {
cal.setTimeInMillis(t);
if (cal.get(DST_OFFSET) > 0) {
return true;
}
}
return false;
}
private static void testSimpleTimeZone(SimpleTimeZone stz) {
if (stz.useDaylightTime() != stz.observesDaylightTime()) {
System.err.printf("Failed: useDaylightTime=%b, observesDaylightTime()=%b%n\t%s%n",
stz.useDaylightTime(),stz.observesDaylightTime(), stz);
errors++;
}
}
}