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8319423: Improve Year.isLeap by checking divisibility by 16

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Reviewed-by: naoto, rriggs
This commit is contained in:
Claes Redestad 2023-11-08 15:18:53 +00:00
parent 59e9981ec2
commit 7d25f1c6cb
6 changed files with 125 additions and 7 deletions
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8
src/java.base/share/classes/sun/util/calendar/CalendarUtils.java
View file

@ -40,8 +40,12 @@ public final class CalendarUtils {
* @see CalendarDate#isLeapYear
*/
public static boolean isGregorianLeapYear(int gregorianYear) {
return (((gregorianYear % 4) == 0) && (((gregorianYear % 100) != 0)
|| ((gregorianYear % 400) == 0)));
// A year that is a multiple of 100, 200 and 300 is not divisible by 16, but 400 is.
// So for a year that's divisible by 4, checking that it's also divisible by 16
// is sufficient to determine it must be a leap year.
return (gregorianYear & 15) == 0
? (gregorianYear & 3) == 0
: (gregorianYear & 3) == 0 && gregorianYear % 100 != 0;
}
/**

2
src/java.base/share/classes/sun/util/calendar/ZoneInfoFile.java
View file

@ -929,7 +929,7 @@ public final class ZoneInfoFile {
}
static final boolean isLeapYear(int year) {
return ((year & 3) == 0) && ((year % 100) != 0 || (year % 400) == 0);
return CalendarUtils.isGregorianLeapYear(year);
}
static final int lengthOfMonth(int year, int month) {