Convert java.time.LocalDate into java.util.Date type

问题

I want to convert java.time.LocalDate into java.util.Date type. Because I want to set the date into JDateChooser. Or is there any date chooser that supports java.time dates?

回答1:

Date date = Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());

That assumes your date chooser uses the system default timezone to transform dates into strings.

回答2:

Here's a utility class I use to convert the newer java.time classes to java.util.Date objects and vice versa:

import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.Date;

public class DateUtils {

  public static Date asDate(LocalDate localDate) {
    return Date.from(localDate.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant());
  }

  public static Date asDate(LocalDateTime localDateTime) {
    return Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
  }

  public static LocalDate asLocalDate(Date date) {
    return Instant.ofEpochMilli(date.getTime()).atZone(ZoneId.systemDefault()).toLocalDate();
  }

  public static LocalDateTime asLocalDateTime(Date date) {
    return Instant.ofEpochMilli(date.getTime()).atZone(ZoneId.systemDefault()).toLocalDateTime();
  }
}

Edited based on @Oliv comment.

回答3:

You can use java.sql.Date.valueOf() method as:

Date date = java.sql.Date.valueOf(localDate);

No need to add time and time zone info here because they are taken implicitly.
See LocalDate to java.util.Date and vice versa simpliest conversion?

回答4:

java.time has the Temporal interface which you can use to create Instant objects from most of the the time classes. Instant represents milliseconds on the timeline in the Epoch - the base reference for all other dates and times.

We need to convert the Date into a ZonedDateTime, with a Time and a Zone, to do the conversion:

LocalDate ldate = ...;
Instant instant = Instant.from(ldate.atStartOfDay(ZoneId.of("GMT")));
Date date = Date.from(instant);

回答5:

In order to create a java.util.Date from a java.time.LocalDate, you have to

add a time to the LocalDate
interpret the date and time within a time zone
get the number of seconds / milliseconds since epoch
create a java.util.Date

The code might look as follows:

LocalDate localDate = LocalDate.now();
Date date = new Date(localDate.atStartOfDay(ZoneId.of("America/New_York")).toEpochSecond() * 1000);

回答6:

This works for me:

java.util.Date d = new SimpleDateFormat("yyyy-MM-dd").parse(localDate.toString());

https://docs.oracle.com/javase/8/docs/api/java/time/LocalDate.html#toString--

回答7:

Kotlin Solution:

1) Paste this extension function somewhere.

fun LocalDate.toDate(): Date = Date.from(this.atStartOfDay(ZoneId.systemDefault()).toInstant())

2) Use it, and never google this again.

val myDate = myLocalDate.toDate()

回答8:

public static Date convertToTimeZone(Date date, String tzFrom, String tzTo) {
    return Date.from(LocalDateTime.ofInstant(date.toInstant(), ZoneId.of(tzTo)).atZone(ZoneId.of(tzFrom)).toInstant());
}

回答9:

Simple

public Date convertFrom(LocalDate date) {
    return java.sql.Timestamp.valueOf(date.atStartOfDay());
}

回答10:

This solution here is a bit longer and you could include something for the time here as well but as far as I understand your problem you just need the actual date.

int day = this.datePicker2.getDate().getDayOfMonth();
int month = this.datePicker2.getDate().getMonthValue();
int year = this.datePicker2.getDate().getYear();
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, month-1);
calendar.set(Calendar.DATE, day);
Date date = calendar.getTime();

Might not look that elegant but it works. Note: month-1 is used because the months in calendar start with 0.

回答11:

java.util.Date.from(localDate.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant());

来源：https://stackoverflow.com/questions/22929237/convert-java-time-localdate-into-java-util-date-type

标签

java

java-8

java-time