java 计时器 - 如何使用 Joda 时间计算两个日期之间的差异？
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Timer - How do I calculate the difference between two dates using Joda Time?
提问by david blaine
I want to get the difference between two times P (start time) and Q (end time) using Joda Time. P and Q could be times on different days or even on the same day. I want to get the difference in format HH-MM-SS, where H=hours, M=minutes, S=seconds.
我想使用 Joda Time 获得两次 P（开始时间）和 Q（结束时间）之间的差异。P 和 Q 可以是不同天甚至同一天的时间。我想获得格式 HH-MM-SS 的差异，其中 H=小时，M=分钟，S=秒。
I want to use this functionality in a timer. I assume that no one will use my timer to measure more than 24 hours.
我想在计时器中使用此功能。我假设没有人会使用我的计时器来测量超过 24 小时。
Please guide me to do this.
请指导我这样做。
回答by IceMan
Take a look at the Joda time FAQ http://joda-time.sourceforge.net/faq.html#datediff
看看 Joda 时间常见问题 http://joda-time.sourceforge.net/faq.html#datediff
And you can use a PeriodFormatterto get the format of your choice. Try the following sample code.
您可以使用 aPeriodFormatter来获取您选择的格式。尝试以下示例代码。
DateTime dt = new DateTime();
DateTime twoHoursLater = dt.plusHours(2).plusMinutes(10).plusSeconds(5);
Period period = new Period(dt, twoHoursLater);
PeriodFormatter HHMMSSFormater = new PeriodFormatterBuilder()
.printZeroAlways()
.minimumPrintedDigits(2)
.appendHours().appendSeparator("-")
.appendMinutes().appendSeparator("-")
.appendSeconds()
.toFormatter(); // produce thread-safe formatter
System.out.println(HHMMSSFormater.print(period));
回答by scottb
I admire the Joda date/time API. It offers some cool functionality and if I needed an immutable calendar or some of the esoteric calendar options it offers, I'd be all over it.
我很欣赏 Joda 日期/时间 API。它提供了一些很酷的功能，如果我需要一个不可变的日历或它提供的一些深奥的日历选项，我会全力以赴。
It is still an external API though.
尽管如此，它仍然是一个外部 API。
So ... why use it when you don't have to. In the Joda API, the "Instant" is the exact same thing as a Java API "Date" (or pretty close to it). These are both thin wrappers around a long that represents an instant in POSIX EPOCH UTC time (which is the number of milliseconds that have elapsed since 00:00am Jan 1, 1970 UTC.
所以......为什么在你不需要的时候使用它。在 Joda API 中，“即时”与 Java API“日期”（或非常接近）完全相同。它们都是围绕 long 的薄包装器，表示 POSIX EPOCH UTC 时间（自 UTC 1970 年 1 月 1 日上午 00:00 以来经过的毫秒数）中的一个瞬间。
If you have either two Instants or two Dates, computing the days between them is trivial, and the Joda library is absolutely not needed for this purpose alone:
如果你有两个 Instants 或两个 Dates，计算它们之间的天数是微不足道的，而且 Joda 库绝对不需要单独用于此目的：
public double computeDaysBetweenDates(Date earlier, Date later) {
long diff;
diff = later.getTime() - earlier.getTime();
return ((double) diff) / (86400.0 * 1000.0);
}
This assumes that the number of seconds in a day is 86400 ... and this is mostly true.
这假设一天中的秒数是 86400 ......这基本上是正确的。
Once you have a difference as a double, it is trivial to convert the fractional portion of the answer (which is the fraction of one day) into HH:MM:SS.
一旦你有一个双精度差，将答案的小数部分（一天的小数）转换成 HH:MM:SS 就很简单了。
