使用新的dateTime API获取持续时间 [英] Getting Duration using the new dateTime API

问题描述

我想获得 实例，

，我发现有两种方式（见下面的代码）。

I want to get a java.time.Duration instance representing the duration of 3 years,
and i found 2 ways to do it (see code below).

public static void main(String[] args) {
    Duration d1 = Duration.of(3, ChronoUnit.YEARS); //Runtime Exception
    Duration d2 = ChronoUnit.YEARS.getDuration().multipliedBy(3);

    System.out.println("d2="+d2.toDays()); //OUTPUT: d2=1095
}

第一种方式 d1 ，在运行时抛出以下异常：

The first way, d1, throws the following Exception at runtime:

Exception in thread "main" java.time.temporal.UnsupportedTemporalTypeException: Unit must not have an estimated duration
    at java.time.Duration.plus(Unknown Source)
    at java.time.Duration.of(Unknown Source)
    at mod7.vehicalc.Test.main(Test.java:26)

第二种方式， d2 ，按预期工作。

The second way, d2, works as expected.

这个差异的原因是什么？

What is the reason for this difference?

推荐答案

code>持续时间是基于时间的时间。

A Duration is a time-based amount of time.

A 期间是基于日期的时间。

A Period is a date-based amount of time.

鉴于这些年份显然是基于日期的，而不是基于时间的，您需要使用期间。 （期间没有复发方面。

Given that years are clearly date-based and not time-based, you need to be using Period. (There is no "recurrance" aspect to Period).

Period p = Period.ofYears(3);

ChronoUnit 的预计持续时间方法主要旨在分类单位，即能说一年一般比一个月多。它不是作为数学计算的基础或创建一个更大的持续时间。特别是，如果您使用期间，则添加到 LocalDate 或 ZonedDateTime 将导致正确答案。如果您使用持续时间，那么您可能会收到意外/错误的答案。

The estimated duration method on ChronoUnit is primarily intended for the purpose of sorting units, ie. being able to say that a year is generally longer than a month. It is not intended to be the basis of mathematical calculations or creating a larger Duration. In particular, if you use a Period then addition to a LocalDate or ZonedDateTime will result in the correct answer. If you use a Duration then you will probably get an unexpected/wrong answer.

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