How to measure elapsed time

Question

I have a 10 and 20 question game  I need to count how much time is passed when a user finishes the game   Timer T new Timer    T scheduleAtFixedRate new TimerTask                   Override     public void run             runOnUiThread new Runnable                                         public void run                                 countdown setText    count                   count                                                       1000  1000     I use this to stop the counter   T cancel      Now I need two things    A way how to count the elapsed time and store it in a variable I need the final value to be a double  for example final score is  15 49 seconds

User · Answer

Even better   long tStart   System nanoTime    long tEnd   System nanoTime    long tRes   tEnd - tStart     time in nanoseconds   Read the documentation about nanoTime

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

User · Answer

Per the Android docs SystemClock elapsedRealtime   is the recommend basis for general purpose interval timing  This is because  per the documentation  elapsedRealtime   is guaranteed to be monotonic         so is the recommend basis for general purpose interval timing    The SystemClock documentation has a nice overview of the various time methods and the applicable use cases for them     SystemClock elapsedRealtime   and SystemClock elapsedRealtimeNanos   are the best bet for calculating general purpose elapsed time  SystemClock uptimeMillis   and System nanoTime   are another possibility  but unlike the recommended methods  they don t include time in deep sleep  If this is your desired behavior then they are fine to use  Otherwise stick with elapsedRealtime    Stay away from System currentTimeMillis   as this will return  wall  clock time  Which is unsuitable for calculating elapsed time as the wall clock time may jump forward or backwards  Many things like NTP clients can cause wall clock time to jump and skew  This will cause elapsed time calculations based on currentTimeMillis   to not always be accurate    When the game starts   long startTime   SystemClock elapsedRealtime      When the game ends   long endTime   SystemClock elapsedRealtime    long elapsedMilliSeconds   endTime - startTime  double elapsedSeconds   elapsedMilliSeconds   1000 0    Also  Timer   is a best effort timer and will not always be accurate  So there will be an accumulation of timing errors over the duration of the game  To more accurately display interim time  use periodic checks to System currentTimeMillis   as the basis of the time sent to setText        Also  instead of using Timer  you might want to look into using TimerTask  this class is designed for what you want to do  The only problem is that it counts down instead of up  but that can be solved with simple subtraction

User · Answer

There are many ways to achieve this  but the most important consideration to measure elapsed time is to use System nanoTime   and TimeUnit NANOSECONDS as the time unit  Why should I do this  Well  it is because System nanoTime   method returns a high-resolution time source  in nanoseconds since some reference point  i e  Java Virtual Machine s start up       This method can only be used to measure elapsed time and is not related to any other notion of system or wall-clock time    For the same reason  it is recommended to avoid the use of the System currentTimeMillis   method for measuring elapsed time  This method returns the wall-clock time  which may change based on many factors  This will be negative for your measurements      Note that while the unit of time of the return value is a millisecond  the granularity of the value depends on the underlying operating system and may be larger   For example  many operating systems measure time in units of tens of milliseconds    So here you have one solution based on the System nanoTime   method  another one using Guava  and the final one Apache Commons Lang  public class TimeBenchUtil       public static void main String   args  throws InterruptedException               stopWatch            stopWatchGuava            stopWatchApacheCommons               public static void stopWatch   throws InterruptedException               long endTime  timeElapsed  startTime   System nanoTime                    the code being measured starts                    sleep for 5 seconds         TimeUnit SECONDS sleep 5                   the code being measured ends                 endTime   System nanoTime                get difference of two nanoTime values         timeElapsed   endTime - startTime           System out println  Execution time in nanoseconds         timeElapsed              public static void stopWatchGuava   throws InterruptedException                  Creates and starts a new stopwatch         Stopwatch stopwatch   Stopwatch createStarted                    the code being measured starts                    sleep for 5 seconds         TimeUnit SECONDS sleep 5                  the code being measured ends                 stopwatch stop       optional             get elapsed time  expressed in milliseconds         long timeElapsed   stopwatch elapsed TimeUnit NANOSECONDS            System out println  Execution time in nanoseconds         timeElapsed              public static void stopWatchApacheCommons   throws InterruptedException               StopWatch stopwatch   new StopWatch            stopwatch start                    the code being measured starts                    sleep for 5 seconds         TimeUnit SECONDS sleep 5                   the code being measured ends                 stopwatch stop          Optional          long timeElapsed   stopwatch getNanoTime             System out println  Execution time in nanoseconds         timeElapsed

User · Answer

When the game starts   long tStart   System currentTimeMillis      When the game ends   long tEnd   System currentTimeMillis    long tDelta   tEnd - tStart  double elapsedSeconds   tDelta   1000 0

[java] How to measure elapsed time

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