Calculating time difference in Milliseconds

Question

I am making a call to a method by passing ipAddress and it will return back the location of ipAddress like Country  City  etc etc  So I was trying to see how much time it is taking for each call  So I set the start time before making call to method and end time after making a call  So sometimes I get difference as 0  And resp contains the valid response    long start time   System currentTimeMillis    resp   GeoLocationService getLocationIp ipAddress   long end time   System currentTimeMillis    long difference   end time-start time    So that means sometimes it is taking 0 ms to get the response back  Any suggestions will be appreciated

User · Answer

In the old days  you know  anytime before yesterday  a PC s BIOS timer would  tick  at a certain interval  That interval would be on the order of 12 milliseconds  Thus  it s quite easy to perform two consecutive calls to get the time and have them return a difference of zero  This only means that the timer didn t  tick  between your two calls  Try getting the time in a loop and displaying the values to the console  If your PC and display are fast enough  you ll see that time jumps  making it look as though it s quantized   Einstein would be upset   Newer PCs also have a high resolution timer  I d imagine that nanoTime   uses the high resolution timer

User · Answer

I do not know how does your PersonalizationGeoLocationServiceClientHelper works  Probably it performs some sort of caching  so requests for the same IP address may return extremely fast

User · Answer

You can use      System nanoTime     To get the result in readable format  use      TimeUnit MILLISECONDS or NANOSECONDS

User · Answer

No  it doesn t mean it s taking 0ms - it shows it s taking a smaller amount of time than you can measure with currentTimeMillis    That may well be 10ms or 15ms  It s not a good method to call for timing  it s more appropriate for getting the current time   To measure how long something takes  consider using System nanoTime instead  The important point here isn t that the precision is greater  but that the resolution will be greater    but only when used to measure the time between two calls  It must not be used as a  wall clock    Note that even System nanoTime just uses  the most accurate timer on your system  - it s worth measuring how fine-grained that is  You can do that like this   public class Test       public static void main String   args  throws Exception            long   differences   new long 5           long previous   System nanoTime            for  int i   0  i  lt  5  i                  long current              while   current   System nanoTime       previous                       Do nothing                              differences i    current - previous              previous   current                                 for  long difference   differences                System out println difference                       On my machine that shows differences of about 466 nanoseconds    so I can t possibly expect to measure the time taken for something quicker than that   And other times may well be roughly multiples of that amount of time

User · Answer

Since Java 1 5  you can get a more precise time value with System nanoTime    which obviously returns nanoseconds instead   There is probably some caching going on in the instances when you get an immediate result

User · Answer

In such a small cases where difference is less than 0 milliseconds you can get difference in nano seconds as well   System nanoTime

User · Answer

Try this  long start time   System nanoTime    resp   GeoLocationService getLocationByIp ipAddress   long end time   System nanoTime    double difference    end time - start time    1e6

User · Answer

I pretty much like the  relatively  new java time library  it s close to awesome  imho   You can calculate a duration between two instants this way   import java time    Instant before   Instant now       do stuff Instant after   Instant now    long delta   Duration between before  after  toMillis        toWhatsoever     API is awesome  highly readable and intuitive   Classes are thread-safe too       References  Oracle Tutorial  Java Magazine

User · Answer

From Java 8 onward you can try the following       import java time    import java time temporal ChronoUnit   Instant start time   Instant now       Your code Instant stop time   Instant now     System out println Duration between start time  stop time  toMillis        or  System out println ChronoUnit MILLIS between start time  stop time

[java] Calculating time difference in Milliseconds

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