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

System.currentTimeMillis() is not safe for elapsed time because this method is sensitive to the system realtime clock changes of the system. You should use System.nanoTime. Please refer to Java System help:

About nanoTime method:

.. This method provides nanosecond precision, but not necessarily nanosecond resolution (that is, how frequently the value changes) - no guarantees are made except that the resolution is at least as good as that of currentTimeMillis()..

If you use System.currentTimeMillis() your elapsed time can be negative (Back <-- to the future)