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January 26, 2023 11:15
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Example implementation of Swiss Bank Holidays in Kotlin
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import BankHoliday.Companion.isBankHoliday | |
import java.time.LocalDate | |
import java.time.Year | |
fun main(args: Array<String>) { | |
// some tests (should be done using JUnit of course ;) | |
mapOf( | |
LocalDate.of(2023, 1, 1) to true, | |
LocalDate.of(2023, 8, 1) to true, | |
LocalDate.of(2023, 12, 25) to true, | |
LocalDate.of(2023, 12, 26) to true, | |
LocalDate.of(2023, 4, 9) to true, | |
LocalDate.of(2023, 4, 7) to true, | |
LocalDate.of(2023, 9, 5) to false, | |
LocalDate.of(2023, 1, 2) to false | |
).forEach { (date, assumption) -> | |
val res = if (date.isBankHoliday() == assumption) "✓" else "×" | |
println("Asserting that $date isBankHoliday should be $assumption: $res") | |
} | |
} | |
// Sealed supertype which can only be implemented from the same file / package | |
sealed class BankHoliday( | |
val date: LocalDate | |
) { | |
companion object { | |
private fun holidays(year: Year) = listOf( | |
Easter(year), | |
AscensionDay(year), | |
EasterMonday(year), | |
GoodFriday(year), | |
WhitMonday(year), | |
BoxingDay(year), | |
ChristmasDay(year), | |
FirstOfJanuary(year), | |
NationalDay(year) | |
) | |
fun LocalDate.isBankHoliday(): Boolean = | |
holidays(Year.of(this.year)).any { h -> | |
this.compareTo(h.date) == 0 | |
} | |
} | |
} | |
class Easter(year: Year) : BankHoliday(calculate(year)) { | |
companion object { | |
private fun calculate(year: Year): LocalDate { | |
val y = year.value | |
val n = y % 19 | |
val c = y / 100 | |
val u = y % 100 | |
val s = c / 4 | |
val t = c % 4 | |
val p = (c + 8) / 25 | |
val q = (c - p + 1) / 3 | |
val e = (19 * n + c - s - q + 15) % 30 | |
val b = u / 4 | |
val d = u % 4 | |
val L = (2 * t + 2 * b - e - d + 32) % 7 | |
val h = (n + 11 * e + 22 * L) / 451 | |
val calculatedMonth = (e + L - 7 * h + 114) / 31 | |
val calculatedDay = (e + L - 7 * h + 114) % 31 + 1 | |
return LocalDate.of(y, calculatedMonth, calculatedDay) | |
} | |
} | |
} | |
// Complex dates based on easter | |
class AscensionDay(year: Year) : BankHoliday( | |
Easter(year) | |
.date | |
.plusDays(39) | |
) | |
class EasterMonday(year: Year) : BankHoliday( | |
Easter(year) | |
.date | |
.plusDays(1) | |
) | |
class GoodFriday(year: Year) : BankHoliday( | |
Easter(year) | |
.date | |
.minusDays(2) | |
) | |
class WhitMonday(year: Year) : BankHoliday( | |
Easter(year) | |
.date | |
.plusDays(50) | |
) | |
// Simple dates | |
class BoxingDay(year: Year) : BankHoliday( | |
year.atMonth(12).atDay(26) | |
) | |
class ChristmasDay(year: Year) : BankHoliday( | |
year.atMonth(12).atDay(25) | |
) | |
class FirstOfJanuary(year: Year) : BankHoliday( | |
year.atMonth(1).atDay(1) | |
) | |
class NationalDay(year: Year) : BankHoliday( | |
year.atMonth(8).atDay(1) | |
) |
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