Difference between System.currentTimeMillis() and Date getTime()?

Question

I was hoping to squeeze a tiny performance gain out of many calls to a function that returns a timestamp. The function looks like this:

public static long get_n         


        

Answer 1

I would suggest running a unit test (ex. https://gist.github.com/ledlogic/8532028). I saw only a slight overall benefit to running the System.currentTimeMillis versus the (new Date()).getTime().

1 billion runs: (1000 outer loops, 1,000,000 inner loops):
    System.currentTimeMillis(): 14.353 seconds
    (new Date()).getTime(): 16.668 seconds

Individual runs would sometimes be slightly biased toward the later approach - depending on your system activity.