我从一个字符串中解析了一个java.util.Date,但它将本地时区设置为date对象的时区。

在解析Date的字符串中没有指定时区。我想设置date对象的特定时区。

我该怎么做呢?


当前回答

在这里,您可以获得日期如“2020-03-11T20:16:17”并返回“11/Mar/2020 - 20:16”

 private String transformLocalDateTimeBrazillianUTC(String dateJson) throws  ParseException {
    String localDateTimeFormat = "yyyy-MM-dd'T'HH:mm:ss";
    SimpleDateFormat formatInput = new SimpleDateFormat(localDateTimeFormat);

    //Here is will set the time zone
    formatInput.setTimeZone(TimeZone.getTimeZone("UTC-03"));

    String brazilianFormat = "dd/MMM/yyyy - HH:mm";
    SimpleDateFormat formatOutput = new SimpleDateFormat(brazilianFormat);
    Date date = formatInput.parse(dateJson);
    return formatOutput.format(date);
}

其他回答

这段代码在我正在开发的应用程序中很有帮助:

    Instant date = null;
    Date sdf = null;
    String formatTemplate = "EEE MMM dd yyyy HH:mm:ss";
    try {
        SimpleDateFormat isoFormat = new SimpleDateFormat("EEE MMM dd yyyy HH:mm:ss");
        isoFormat.setTimeZone(TimeZone.getTimeZone(ZoneId.of("US/Pacific")));
        sdf = isoFormat.parse(timeAtWhichToMakeAvailable);
        date = sdf.toInstant();

    } catch (Exception e) {
        System.out.println("did not parse: " + timeAtWhichToMakeAvailable);
    }

    LOGGER.info("timeAtWhichToMakeAvailable: " + timeAtWhichToMakeAvailable);
    LOGGER.info("sdf: " + sdf);
    LOGGER.info("parsed to: " + date);

如果你必须只使用标准JDK类,你可以使用这个:

/**
 * Converts the given <code>date</code> from the <code>fromTimeZone</code> to the
 * <code>toTimeZone</code>.  Since java.util.Date has does not really store time zome
 * information, this actually converts the date to the date that it would be in the
 * other time zone.
 * @param date
 * @param fromTimeZone
 * @param toTimeZone
 * @return
 */
public static Date convertTimeZone(Date date, TimeZone fromTimeZone, TimeZone toTimeZone)
{
    long fromTimeZoneOffset = getTimeZoneUTCAndDSTOffset(date, fromTimeZone);
    long toTimeZoneOffset = getTimeZoneUTCAndDSTOffset(date, toTimeZone);

    return new Date(date.getTime() + (toTimeZoneOffset - fromTimeZoneOffset));
}

/**
 * Calculates the offset of the <code>timeZone</code> from UTC, factoring in any
 * additional offset due to the time zone being in daylight savings time as of
 * the given <code>date</code>.
 * @param date
 * @param timeZone
 * @return
 */
private static long getTimeZoneUTCAndDSTOffset(Date date, TimeZone timeZone)
{
    long timeZoneDSTOffset = 0;
    if(timeZone.inDaylightTime(date))
    {
        timeZoneDSTOffset = timeZone.getDSTSavings();
    }

    return timeZone.getRawOffset() + timeZoneDSTOffset;
}

功劳归于这篇文章。

calendar是使用JDK类处理时区的常用方法。Apache Commons还有一些可能有用的替代方案/实用程序。Edit Spong的留言提醒我,我听说Joda-Time真的很不错(尽管我自己没有用过)。

将日期转换为字符串,并使用SimpleDateFormat。

    SimpleDateFormat readFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
    readFormat.setTimeZone(TimeZone.getTimeZone("GMT" + timezoneOffset));
    String dateStr = readFormat.format(date);
    SimpleDateFormat writeFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
    Date date = writeFormat.parse(dateStr);

您还可以在JVM级别设置时区

Date date1 = new Date();
System.out.println(date1);

TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
// or pass in a command line arg: -Duser.timezone="UTC"

Date date2 = new Date();
System.out.println(date2);

输出:

Thu Sep 05 10:11:12 EDT 2013
Thu Sep 05 14:11:12 UTC 2013