在Java中将纪元转换为ZonedDateTime

问题描述

如何在Java中将类似 1413225446.92000 的时代转换为 ZonedDateTime ？

How to convert epoch like 1413225446.92000 to ZonedDateTime in java?

给出的代码期望 long 值，因此对于上面给出的值，这将引发 NumberFormatException 。

The code given expects long value hence this will throw NumberFormatException for the value given above.

ZonedDateTime.ofInstant(Instant.ofEpochMilli(Long.parseLong(dateInMillis)), ZoneId.of(TIME_ZONE_PST));

推荐答案

是一个很好的答案。从小数部分中取出纳秒到一个纳秒整数可能会导致一个或两个陷阱。我建议：

Basil Bourque’s answer is a good one. Taking out the nanoseconds from the fractional part into an integer for nanoseconds may entail a pitfall or two. I suggest:

    String dateInMillis = "1413225446.92000";
    String[] secondsAndFraction = dateInMillis.split("\\.");
    int nanos = 0;
    if (secondsAndFraction.length > 1) { // there’s a fractional part
        // extend fractional part to 9 digits to obtain nanoseconds
        String nanosecondsString
                = (secondsAndFraction[1] + "000000000").substring(0, 9);
        nanos = Integer.parseInt(nanosecondsString);
        // if the double number was negative, the nanos must be too
        if (dateInMillis.startsWith("-")) {
            nanos = -nanos;
        }
    }
    ZonedDateTime zdt = Instant
            .ofEpochSecond(Long.parseLong(secondsAndFraction[0]), nanos)
            .atZone(ZoneId.of("Asia/Manila"));
    System.out.println(zdt);

此打印文件

2014-10-14T02:37:26.920+08:00[Asia/Manila]

纳秒不需要64位，所以我只是使用 int 。

We don’t need 64 bits for the nanoseconds, so I am just using an int.

假设：我假设您的字符串包含浮点数，并且可以对它进行签名，例如 -1.50 表示前一秒半时代。如果有一天的纪元用科学记数法（1.41322544692E9）表示，则上述方法将无效。

Assumption: I have assumed that your string contains a floating-point number and that it may be signed, for example -1.50 would mean one and a half seconds before the epoch. If one day your epoch time comes in scientific notation (1.41322544692E9), the above will not work.

请在地区/城市中替换您所需的时区格式（如果不是亚洲/马尼拉），例如America / Vancouver，America / Los_Angeles或Pacific / Pitcairn。避免使用三个字母缩写，例如PST，它们是模棱两可的，通常不是真实的时区。

Please substitute your desired time zone in the region/city format if it didn’t happen to be Asia/Manila, for example America/Vancouver, America/Los_Angeles or Pacific/Pitcairn. Avoid three letter abbreviations like PST, they are ambiguous and often not true time zones.

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