英文:
Parse list of dates to list string in scala
问题
import org.joda.time.LocalDate
import org.joda.time._
def getDates(startDate: String, endDate: String): Any = {
val from = LocalDate.parse(startDate)
val until = LocalDate.parse(endDate)
val numberOfDays = Days.daysBetween(from, until).getDays()
for (f <- 0 to numberOfDays) yield from.plusDays(f)
}
println(getDates("20200101", "20200131"))
// This returns -> Vector(2020-01-01, 2020-01-31)
// Need to convert returned Vector to List[String] in which elements are of format "yyyyMMdd"
val dateList = getDates("20200101", "20200131").map(date => date.toString("yyyyMMdd")).toList
// Expected Output: List(20200101, ...., 20200131)
英文:
Need to format date according to yyyyMMdd
below code generates a list of dates
import org.joda.time.LocalDate
import org.joda.time._
def getDates(startDate: String,endDate: String): Any = {
val from = LocaDate.parse(startDate)
val until = LocalDate.parse(endDate)
val numberOfDays = Days.daysBetween(from, until).getDays()
for (f<- 0 to numberOfDays) yield from.plusDays(f)
}
println(getDates("20200101","20200131"))
This returns -> Vector(2020-01-01,2020-01-31)
Need to convert returned Vector to List[String] in which elements are of format "yyyyMMdd"
Expected Output: List(20200101,....,20200131)
答案1
得分: 2
如果getDates()的输入是2个字符串，并且期望的输出是List[String]，那么我真的看不出使用旧的过时的Joda Time库的任何理由。java.time库更新且功能更丰富。
它还提供了datesUntil()方法，基本上可以实现您想要的功能，只是它返回一个java.util.stream.Stream，从Java Stream转换为Scala List会有点麻烦，这取决于您正在使用的Scala版本。
以下是一个示例，在Scala 2.13.x中如何实现：
import java.time.LocalDate
import java.time.format.DateTimeFormatter
import scala.jdk.StreamConverters.StreamHasToScala
def getDates(startDate: String, endDate: String): List[String] = {
val pattern = DateTimeFormatter.ofPattern("yyyyMMdd")
LocalDate.parse(startDate, pattern)
.datesUntil(LocalDate.parse(endDate, pattern).plusDays(1))
.toScala(List)
.map(_.format(pattern))
}
您会注意到，此示例没有对有效输入格式进行检查，因此这仅用于演示，不适用于生产环境的代码。
英文:
If the getDates() input is 2 strings, and the desired output is List[String], then I don't really see any reason to use the old and outdated Joda Time library. The java.time library is more recent and feature-full.
It also offers the datesUntil() method, which does pretty much what you want, except that it returns a java.util.stream.Stream, which is a bit of a pain because the transition from Java Stream to Scala List will depend on the Scala version you're running.
Here, for example, is how you might do it in Scala 2.13.x:
import java.time.LocalDate
import java.time.format.DateTimeFormatter
import scala.jdk.StreamConverters.StreamHasToScala
def getDates(startDate:String, endDate:String):List[String] = {
val pattern = DateTimeFormatter.ofPattern("yyyyMMdd")
LocalDate.parse(startDate, pattern)
.datesUntil(LocalDate.parse(endDate, pattern).plusDays(1))
.toScala(List)
.map(_.format(pattern))
}
You'll notice that there is no checking for valid input format, so this is for demonstration and not production-worthy code.
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