Duration.between对ChronoUnit.between

Question

这两种方法是等价的吗？

版本1:

var diff = Duration.between(begin, end).toHours();

版本2;

var diff = ChronoUnit.HOURS.between(begin, end);

有什么隐含的区别吗？如果是，我应该选择哪一种？

Answer 1

开放JDK 15的分析实现

A) Duration.between(begin，end).toHours();

Duration.between(begin, end)优先呼叫

long until(Temporal endExclusive, TemporalUnit unit); //called with unit of NANOS or SECONDS if first one fails

然后分析差异，根据已计算的nanos创建一个Duration (如果nanos计算失败，则创建秒)。

public static Duration between(Temporal startInclusive, Temporal endExclusive) {
        try {
            return ofNanos(startInclusive.until(endExclusive, NANOS));
        } catch (DateTimeException | ArithmeticException ex) {
            long secs = startInclusive.until(endExclusive, SECONDS);
            long nanos;
            try {
                nanos = endExclusive.getLong(NANO_OF_SECOND) - startInclusive.getLong(NANO_OF_SECOND);
                if (secs > 0 && nanos < 0) {
                    secs++;
                } else if (secs < 0 && nanos > 0) {
                    secs--;
                }
            } catch (DateTimeException ex2) {
                nanos = 0;
            }
            return ofSeconds(secs, nanos);
        }

然后，您必须调用toHours()，然后解析创建的Duration对象以返回小时数。

B) ChronoUnit.HOURS.between(开始，结束)；

直接呼叫

long until(Temporal endExclusive, TemporalUnit unit);

//But instead of the implementation before, now it is called with unit of HOURS directly

直接返回时间一样长的时间。

实现的比较

两者的工作方式相同(至少几个小时)，结果也是一样的。

但是对于A，，我们似乎有一些不需要的来回转换。

解决方案B看起来很直接，没有任何我们不需要的转换

答案

我会选择B作为更有效率的

Answer 2

这两种方法似乎最终都调用了Temporal#until

var diff = Duration.between(begin，end).toHours();

Duration#between
\
 Temporal#until (used twice but some branching go for another implementation)

var diff =ChronoUnit.HOURS.between(开始，结束)；

ChronoUnit.HOURS#between
\
 Temporal#until (it is the only method underlying)