java - Guava Stopwatch类有什么优势？

Question

在 Google Guava 库中，有一个 Stopwatch 类，它的 documentation说明这一点 -

An object that measures elapsed time in nanoseconds. It is useful to measure elapsed time using this class instead of direct calls to System.nanoTime() for a few reasons:

1. An alternate time source can be substituted, for testing or performance reasons.
2. As documented by nanoTime, the value returned has no absolute meaning, and can only be interpreted as relative to another timestamp returned by nanoTime at a different time. Stopwatch is a more effective abstraction because it exposes only these relative values, not the absolute ones.

问题 - 他们指的这个“备用时间源”是什么？ JRE/JVM 是否也提供此选项？

Answer 1

请参阅 Stopwatch(Ticker) 构造函数。提供您自己的 Ticker 允许您制作一个秒表，该秒表会产生用于测试目的的可预测结果。