In Scala - How to get the day of the week?

问题

Suppose my date format is 21/05/2017 then the output will be SUN.

How can I get the day given a date?

回答1:

    import java.time.LocalDate
    import java.time.format.DateTimeFormatter

    val df = DateTimeFormatter.ofPattern("dd/MM/yyyy")
    val dayOfWeek = LocalDate.parse("21/05/2017",df).getDayOfWeek

回答2:

You can use SimpleDateFormat as illustrated below:

import java.util.Calendar
import java.text.SimpleDateFormat

val now = Calendar.getInstance.getTime

val date = new SimpleDateFormat("yyyy-MM-dd")
date.format(now)
res1: String = 2017-05-20

val dowInt = new SimpleDateFormat("u")
dowInt.format(now)
res2: String = 6

val dowText = new SimpleDateFormat("E")
dowText.format(now)
res3: String = Sat

[UPDATE]

As per comments below, please note that SimpleDateFormat isn't thread-safe.

回答3:

You can also use nscala-time which is a Scala wrapper for Java's joda-time which is a datetime library with a ton of functionality.

import com.github.nscala_time.time.Imports._

val someDate =(newDateTime).withYear(2017)
                           .withMonthOfYear(5)
                           .withDayOfMonth(21)

someDate.getDayOfWeek

res7: Int = 7

Now you need to know the mapping between integer days of the week and names. Here, 7 corresponds to Sunday.

来源：https://stackoverflow.com/questions/44089758/in-scala-how-to-get-the-day-of-the-week