Joda的“负”持续时间，错误或功能？ [英] 'negative' Duration in Joda, a bug or a feature?

问题描述

尝试比较两个DateTime时，我写了这段代码

When trying to compare two DateTime I wrote this code

private boolean compareTime(DateTime dt1, DateTime dt2) 
{ 
    long d1 = (new Duration(dt1.getMillis() - dt2.getMillis())).getMillis();
    long d2 = Duration.standardHours(1).getMillis(); 
    return  d1  < d2; 
}
DateTime dt1 = new DateTime();
Thread.sleep(250);
DateTime dt2 = dt1.plusHours(2);
System.out.println(compareTime(dt1,dt2));
System.out.println(compareTime(dt2,dt1));

期望此打印

false
false

但这是

true
false

因此，当我查看持续时间CTOR时，发现它实际上创建了一个带有负毫秒持续时间的持续时间（getMils（）返回-ve）。

So when I looked into Duration CTOR, then turned out it actually created a Duration with negative millisecond duration (getMils() returns -ve).

什么是-ve持续时间的含义是什么？
（为了保持客观性）
这是Bug还是功能？

What is the meaning of -ve Duration ? (To keep it very objective) Is this a bug or a feature ?

推荐答案

听起来对我完全明智。您将负数毫秒传递给构造函数-为什么您要期望变为正数？

Sounds entirely sensible to me. You're passing a negative number of milliseconds into the constructor - why would you expect that to become positive?

负持续时间就是负时间量-例如，从现在到过去某个时间的时间。它允许进行明智的算术运算：

A negative duration is simply a negative amount of time - the time from "now" to "some time in the past", for example. It allows sensible arithmetic:

Instant x = ...;
Instant y = ...;
// Duration from x to y, although the result isn't "anchored" (it forgets x and y)
Duration d = new Duration(x, y);
Instant y2 = x.plus(d); // y2 is now equal to y

没有持续时间，这是不可能的。

Without negative durations, this would be impossible.

如果您始终希望持续时间为非负数，只需致电 Math.abs -否则，请不要使用持续时间对于 d1 ：

If you always want a non-negative duration, just call Math.abs - or in your case, don't use Duration at all for d1:

long d1 = Math.Abs(dt1.getMillis() - dt2.getMillis());

这篇关于Joda的“负”持续时间，错误或功能？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！