68 lines
2.6 KiB
Plaintext
68 lines
2.6 KiB
Plaintext
When creating a ``++DateTimeFormatter++`` using the ``++WeekFields.weekBasedYear()++`` temporal field, the resulting year number may be off by 1 at the beginning of a new year (when the date to format is in a week that is shared by two consecutive years).
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Using this year number in combination with an incompatible week temporal field yields a result that may be confused with the first week of the previous year.
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Instead, when paired with a week temporal field, the week-based year should only be used with the week of week-based year temporal field ``++WeekFields.weekOfWeekBasedYear()++``.
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Alternatively the temporal field ``++ChronoField.ALIGNED_WEEK_OF_YEAR++`` can be used together with a regular year (but not the week based year).
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== Noncompliant Code Example
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----
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new DateTimeFormatterBuilder()
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.appendValue(ChronoField.YEAR, 4) // Noncompliant: using week of week-based year with regular year
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.appendLiteral('-')
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.appendValue(WeekFields.ISO.weekOfWeekBasedYear(), 2)
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.toFormatter();
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new DateTimeFormatterBuilder()
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.appendValue(ChronoField.YEAR_OF_ERA, 4) // Noncompliant: using week of week-based year with regular year
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.appendLiteral('-')
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.appendValue(WeekFields.ISO.weekOfWeekBasedYear(), 2)
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.toFormatter();
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new DateTimeFormatterBuilder()
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.appendValue(WeekFields.ISO.weekBasedYear(), 4) // Noncompliant: using aligned week of year with week-based year
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.appendLiteral('-')
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.appendValue(ChronoField.ALIGNED_WEEK_OF_YEAR, 2)
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.toFormatter();
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----
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Here the first two formatters would wrongly format the 1st of January 2016 as "2016-53" while the last one would format it as "2015-01"
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== Compliant Solution
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----
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new DateTimeFormatterBuilder()
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.appendValue(WeekFields.ISO.weekBasedYear(), 4)
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.appendLiteral('-')
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.appendValue(WeekFields.ISO.weekOfWeekBasedYear(), 2)
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.toFormatter();
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new DateTimeFormatterBuilder()
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.appendValue(ChronoField.YEAR, 4)
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.appendLiteral('-')
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.appendValue(ChronoField.ALIGNED_WEEK_OF_YEAR, 2)
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.toFormatter();
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new DateTimeFormatterBuilder()
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.appendValue(ChronoField.YEAR_OF_ERA, 4)
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.appendLiteral('-')
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.appendValue(ChronoField.ALIGNED_WEEK_OF_YEAR, 2)
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.toFormatter();
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----
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Here the first formatter would format the 1st of January 2016 as "2015-53" while the last two would produce "2016-01", both of which are correct depending on how you count the weeks.
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== Exceptions
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No issue is raised when week-based year is not used in combination with a week temporal field.
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Similarly, no issue is raised if week of week-based year is not used in combination with a year temporal field.
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