System.currentTimeMillis vs System.nanoTime

Question

Accuracy Vs. Precision

What I would like to know is whether I should use System.currentTimeMillis() or System.nanoTime()<

Answer 1

Update by Arkadiy: I've observed more correct behavior of System.currentTimeMillis() on Windows 7 in Oracle Java 8. The time was returned with 1 millisecond precision. The source code in OpenJDK has not changed, so I do not know what causes the better behavior.

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David Holmes of Sun posted a blog article a couple years ago that has a very detailed look at the Java timing APIs (in particular System.currentTimeMillis() and System.nanoTime()), when you would want to use which, and how they work internally.

Inside the Hotspot VM: Clocks, Timers and Scheduling Events - Part I - Windows

One very interesting aspect of the timer used by Java on Windows for APIs that have a timed wait parameter is that the resolution of the timer can change depending on what other API calls may have been made - system wide (not just in the particular process). He shows an example where using Thread.sleep() will cause this resolution change.