Java8 has new date and time classes to “replace” the old not-so-beloved java.util.Date class.
Unfortunately though, converting between the two is somewhat less obvious than you might expect.
Convert java.util.Date to java.time.LocalDateTime
Date ts = ...; Instant instant = Instant.ofEpochMilli(ts.getTime()); LocalDateTime res = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()); |
The big trick (for all these conversions) is to convert to Instant. This can be converted to LocalDateTime by telling the system which timezone to use. This needs to be the system default locale, otherwise the time will change.
Convert java.util.Date to java.time.LocalDate
Date date = ...; Instant instant = Instant.ofEpochMilli(date.getTime()); LocalDate res = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalDate(); |
Convert java.util.Date to java.time.LocalTime
Date time = ...; Instant instant = Instant.ofEpochMilli(time.getTime()); LocalTime res = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalTime(); |
Convert java.time.LocalDateTime to java.util.Date
LocalDateTime ldt = ...; Instant instant = ldt.atZone(ZoneId.systemDefault()).toInstant(); Date res = Date.from(instant); |
Convert java.time.LocalDate to java.util.Date
LocalDate ld = ...;Instant instant = ld.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant(); Date res = Date.from(instant); |
Convert java.time.LocalTime to java.util.Date
LocalTime lt = ...; Instant instant = lt.atDate(LocalDate.of(A_YEAR, A_MONTH, A_DAY)). atZone(ZoneId.systemDefault()).toInstant(); Date time = Date.from(instant); |
This one is a little, funny, you need to inject a date to convert the time… Gives you the option of start of epoch or something else.
Converting from java.util.Date to an Instant is even easier: There’s a method toInstant() in the Date class that just returns Instant.ofEpochMilli(getTime()) as you posted.
How to convert a LocalDate to an Instant?
I get an exception with
LocalDate date = LocalDate.of(2012, 2, 2);
Instant instant = Instant.from(date);
@ric
I wondered about that myself. Incredibly insane API design that has no good explanation what so ever.
It turns out you need to do something like this:
date.atZone(ZoneId.systemDefault()).toInstant()
4 years of bloody API development for one to have to do this
Date.from(date.atZone(ZoneId.systemDefault()).toInstant()) to convert a LocalDate to Date
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