Scala convert a DateTime value to Timestamp - scala

Question

maybe it is a duplicated question, I tried to find a solution but no way.
Problem : convert a DateTime instance to Timestamp.
My DateTime instance is created as :
import org.joda.time.DateTime
val start = (new DateTime).withYear(2016)
.withMonthOfYear(12)
.withDayOfMonth(1)
.withMinuteOfHour(0)
.withHourOfDay(0)
with println of this date, I got :
2016-12-01T00:00:18.856+01:00
What I need is like Epoch timestamp in picture bellow :

Answer 1

IMHO one of the fastest way to calculate the Epoch timestamp is:
scala> :paste
// Entering paste mode (ctrl-D to finish)
def epochDayForYear(year: Int): Long =
365L * year + (((year + 3) >> 2) - (if (year < 0) {
val century = year * 1374389535L >> 37 // divide int by 100 (a sign correction is not required)
century - (century >> 2)
} else ((year + 99) * 1374389535L >> 37) - ((year + 399) * 1374389535L >> 39))) // divide int by 100 and by 400 accordingly (a sign correction is not required)
def dayOfYearForYearMonth(year: Int, month: Int): Int =
((month * 1050835331877L - 1036518774222L) >> 35).toInt - // == (367 * month - 362) / 12
(if (month <= 2) 0
else if (isLeap(year)) 1
else 2)
def isLeap(year: Int): Boolean = (year & 3) == 0 && {
val century = (year * 1374389535L >> 37).toInt - (year >> 31) // divide int by 100
century * 100 != year || (century & 3) == 0
}
def secondOfDay(hour: Int, month: Int, day: Int): Int =
hour * 3600 + month * 60 + day
val (year, month, day, hour, minute, second, timeZoneOffsetHour, timeZoneOffsetMinute) =
(2016, 12, 1, 0, 0, 2, 0, 0)
val epochSecond =
(epochDayForYear(year) + (dayOfYearForYearMonth(year, month) + day - 719529)) * 86400 +
secondOfDay(hour + timeZoneOffsetHour, minute + timeZoneOffsetMinute, second) // where 719528 is days 0000 to 1970
// Exiting paste mode, now interpreting.
epochDayForYear: (year: Int)Long
dayOfYearForYearMonth: (year: Int, month: Int)Int
isLeap: (year: Int)Boolean
secondOfDay: (hour: Int, month: Int, day: Int)Int
year: Int = 2016
month: Int = 12
day: Int = 1
hour: Int = 0
minute: Int = 0
second: Int = 2
timeZoneOffsetHour: Int = 0
timeZoneOffsetMinute: Int = 0
epochSecond: Long = 1480550402
BTW, most of this code is borrowed from the jsoniter-scala project.

Answer 2

Using java.time. Does this help?
scala> val x = java.time.LocalDateTime.ofEpochSecond(System.currentTimeMillis/1000,0,java.time.ZoneOffset.UTC)
x: java.time.LocalDateTime = 2018-11-21T18:41:29
scala> java.time.LocalDateTime.parse("2018-11-21T18:41:29.123").toEpochSecond(java.time.ZoneOffset.UTC)
res41: Long = 1542825689
scala> java.time.LocalDateTime.parse("2018-11-21T18:41:29.123").format(java.time.format.DateTimeFormatter.ofPattern("eeee, MMMM dd, yyyy hh:mm:ss a"))
res61: String = Wednesday, November 21, 2018 06:41:29 PM
scala>
This link https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html might be helpful to know the symbols used in the format options

Answer 3

First: Scala gets compiled into Java, so when you are asking a question about a Java library you can use examples from that.
Second: Do you have any default Timezone in your application? I would put this in a logical place (i.e. when you start you application / in some config)
DateTimeZone.setDefault(DateTimeZone.UTC);
Now you can just create a new java.sql.Timestamp like this:
import java.sql.Timestamp;
import java.time.Instant
val start = (new DateTime).withYear(2016)
.withMonthOfYear(12)
.withDayOfMonth(1)
.withMinuteOfHour(0)
.withHourOfDay(0)
val timestamp = new Timestamp(start.getMillis()) : Timestamp
// To get the epoch timestamp, take a look at java.time.Instant
val epochTimestamp = timestamp.toInstant() : Instant
More information here: https://www.jeejava.com/conversion-of-joda-date-time-to-sql-timestamp-and-vice-versa/