格式化时间后的奇怪输出(以毫秒为单位)

问题描述：

我想使用代码将 1574348400 的值转换为日期格式:

I want to convert 1574348400 value to date format using code:

public class Main {

    public Main() {
        long value = 1574348400;
        String dateString = new SimpleDateFormat("EEEE dd MMMM, yyyy").format(new Date(value));
        System.out.println("Formated time: " + dateString);
    }

    public static void main(String[] args) {
        new Main();
    }
}

我想得到的输出为: 2019年11月20日星期三，但是我要获得 1970年1月19日星期一.如何获取当前日期而不是1970年的日期?

I want to get the output as: Wednesday 20 November, 2019 but I'm getting Monday 19 January, 1970. How to get the current date not the 1970's date?

答

使用 java.time 解析您的时间(以秒为单位)，它提供了一种以秒为单位的方法...

Parse your time (in seconds) using java.time, it provides a method for epoch seconds...

public static void main(String[] args) {
    // your seconds
    long seconds = 1574348400;
    // same in millis
    long millis = 1574348400000L;

    // find out the zone of your system
    ZoneId systemDefaultZoneId = ZoneId.systemDefault();
    // or set a specific one
    ZoneId utcZoneId = ZoneId.of("UTC");

    // parse a ZonedDateTime of your system default time zone from the seconds
    ZonedDateTime fromSecsSysDefZone = ZonedDateTime.ofInstant(Instant.ofEpochSecond(seconds),
                                                        systemDefaultZoneId);
    // parse a ZonedDateTime of UTC from the seconds
    ZonedDateTime fromSecsUtc = ZonedDateTime.ofInstant(Instant.ofEpochSecond(seconds),
                                                        utcZoneId);
    // parse a ZonedDateTime of your system default time zone from the milliseconds
    ZonedDateTime fromMillisSysDefZone = ZonedDateTime.ofInstant(Instant.ofEpochMilli(millis),
                                                        systemDefaultZoneId);
    // parse a ZonedDateTime of UTC from the milliseconds
    ZonedDateTime fromMillisUtc = ZonedDateTime.ofInstant(Instant.ofEpochMilli(millis),
                                                        utcZoneId);

    // print the ones that were created using your default time zone
    System.out.println("from seconds:\t"
            + fromSecsSysDefZone.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
    System.out.println("from millis:\t"
            + fromMillisSysDefZone.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
    // print a check for equality
    System.out.println("Both ZonedDateTimes are "
            + (fromSecsSysDefZone.equals(fromMillisSysDefZone) ? "equal" : "different"));

    System.out.println("————————————————————————————————");

    // print the ones that were created using UTC
    System.out.println("from seconds:\t"
            + fromSecsUtc.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
    System.out.println("from millis:\t"
            + fromMillisUtc.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
    // print a check for equality
    System.out.println("Both ZonedDateTimes are "
            + (fromSecsUtc.equals(fromMillisUtc) ? "equal" : "different"));
}

此代码(在我的系统上)产生的输出是

The output produced by this code (on my system) is

from seconds:   2019-11-21T16:00:00+01:00[Europe/Berlin]
from millis:    2019-11-21T16:00:00+01:00[Europe/Berlin]
Both ZonedDateTimes are equal
————————————————————————————————
from seconds:   2019-11-21T15:00:00Z[UTC]
from millis:    2019-11-21T15:00:00Z[UTC]
Both ZonedDateTimes are equal

如果您必须使用Java 6或7，则可以在Github上使用 ThreeTenBackport-Project，它在这两个旧版本中启用了 java.time 的(大多数)功能.
在单独的网站上说明.

If you have to use Java 6 or 7, then you can use the ThreeTenBackport-Project on Github, which enables (most) functionality of java.time in those two older versions.
Its use is explained on a separate website.

格式化时间后的奇怪输出(以毫秒为单位)

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