Extra milliseconds from Calendar.getInstance.getTimeInMillis - scala

Question

So, I had an innocent little snippet like
import java.util.Calendar
import java.sql.Timestamp
val cal = Calendar.getInstance
cal.set(1968, Calendar.APRIL, 25, 0, 45, 0)
val time = cal.getTimeInMillis
new java.sql.Timestamp(time)
new java.sql.Date(time).formatted("%1$tY-%1$tm-%1$te %1$tH:%1$tM:%1$tS.%1$tL")
and it kept showing me non-zero millisecond values. I was trying to construct a SQL timestamp in a test to compare to the output of a function, so it was a bit of a problem. I couldn't set an exact time -- there's no Calendar.setMillis API.

Answer 1

Or you could use the more recent and up-to-date java.time library.
import java.time.LocalDateTime
import java.time.ZoneId
val time = LocalDateTime.of(1968, 4, 25, 0, 45, 0) //date/time of interest
.atZone(ZoneId.systemDefault()) //this time zone
.toInstant().toEpochMilli() //in milliseconds
new java.sql.Timestamp(time)
//res0: java.sql.Timestamp = 1968-04-25 00:45:00.0
new java.sql.Date(time).formatted("%1$tY-%1$tm-%1$te %1$tH:%1$tM:%1$tS.%1$tL")
//res1: String = 1968-04-25 00:45:00.000

Answer 2

Calendar.getInstance always contains the current time. Subsequently calling 'set' on it overrides the year, month, day, hour, minute and second on it, but not the number of milliseconds. You have to zero those out yourself.
import java.util.Calendar
import java.sql.Timestamp
val cal = Calendar.getInstance
cal.set(1968, Calendar.APRIL, 25, 0, 45, 0)
val millis = cal.getTimeInMillis
val time = millis - millis % 1000
new java.sql.Timestamp(time)
new java.sql.Date(time).formatted("%1$tY-%1$tm-%1$te %1$tH:%1$tM:%1$tS.%1$tL")