Measure execution time for a Java method

Question

How do I calculate the time taken for the execution of a method in Java

User · Answer

You might want to think about aspect-oriented programming. You don't want to litter your code with timings. You want to be able to turn them off and on declaratively.

If you use Spring, take a look at their MethodInterceptor class.

User · Answer

To be more precise  I would use nanoTime   method rather than currentTimeMillis     long startTime   System nanoTime    myCall     long stopTime   System nanoTime    System out println stopTime - startTime     In Java 8  output format is ISO-8601     Instant start   Instant now    Thread sleep 63553   Instant end   Instant now    System out println Duration between start  end       prints PT1M3 553S   Guava Stopwatch   Stopwatch stopwatch   Stopwatch createStarted    myCall    stopwatch stop       optional System out println  Time elapsed     stopwatch elapsed TimeUnit MILLISECONDS

User · Answer

You can take timestamp snapshots before and after  then repeat the experiments several times to average to results  There are also profilers that can do this for you   From  quot Java Platform Performance  Strategies and Tactics quot  book  With System currentTimeMillis   class TimeTest1      public static void main String   args           long startTime   System currentTimeMillis           long total   0        for  int i   0  i  lt  10000000  i               total    i                 long stopTime   System currentTimeMillis          long elapsedTime   stopTime - startTime        System out println elapsedTime           With a StopWatch class You can use this StopWatch class  and call start   and stop before and after the method  class TimeTest2      public static void main String   args           Stopwatch timer   new Stopwatch   start           long total   0        for  int i   0  i  lt  10000000  i               total    i                 timer stop          System out println timer getElapsedTime             See here  archived    NetBeans Profiler   Application Performance Application Performance profiles method-level CPU performance  execution time   You can choose to profile the entire application or a part of the application   See here

User · Answer

Check this  System currentTimeMillis   With this you can calculate the time of your method by doing   long start   System currentTimeMillis    class method    long time   System currentTimeMillis   - start

User · Answer

As proposed nanoTime    is very precise on short time scales  When this precision is required you need to take care about what you really measure  Especially not to measure the nanotime call itself  long start1   System nanoTime       maybe add here a call to a return to remove call up time  too     Avoid optimization  long start2   System nanoTime    myCall     long stop   System nanoTime    long diff   stop - 2 start2   start1   System out println diff     ns      By the way  you will measure different values for the same call due to   other load on your computer  background  network  mouse movement  interrupts  task switching  threads  cache fillings  cold  warm  jit compiling  no optimization  performance hit due to running the compiler  performance boost due to compiler  but sometimes code with jit is slower than without

User · Answer

If you are currently writing the application  than the answer is to use System currentTimeMillis or System nanoTime serve the purpose as pointed by people above    But if you have already written the code  and you don t want to change it its better to use Spring s method interceptors  So for instance your service is    public class MyService        public void doSomething             for  int i   1  i  lt  10000  i                  System out println  i     i                       To avoid changing the service  you can write your own method interceptor   public class ServiceMethodInterceptor implements MethodInterceptor       public Object invoke MethodInvocation methodInvocation  throws Throwable           long startTime   System currentTimeMillis            Object result   methodInvocation proceed            long duration   System currentTimeMillis   - startTime          Method method   methodInvocation getMethod            String methodName   method getDeclaringClass   getName           method getName            System out println  Method      methodName      took     duration     milliseconds to run            return null            Also there are open source APIs available for Java  e g  BTrace  or Netbeans profiler as suggested above by  bakkal and  Saikikos  Thanks

User · Answer

Nanotime is in fact not even good for elapsed time because it drifts away signficantly more than currentTimeMillis   Furthermore nanotime tends to provide excessive precision at the expense of accuracy   It is therefore highly inconsistent and needs refinement   For any time measuring process currentTimeMillis  though almost as bad   does better in terms of balancing accuracy and precision

User · Answer

In case you develop applications for Android you should try out the TimingLogger class  Take a look at these articles describing the usage of the TimingLogger helper class    Measuring performance in the Android SDK  27 09 2010  Discovering the Android API - Part 1  03 01 2017

[java] Measure execution time for a Java method

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