calculate time of a method execution in java
To calculate execution time without using AOP, Reflection and no changes in the method code, This might help you.
You have ruled out all practical options apart from running your code using a profiler that can instrument the code and measure elapsed time for the calls.
However, I would note that profiling is only going to be viable if this code is used in an (exist) application that repeatedly calls the methods. Even then, since the methods are so short, getting reliable measurements will be difficult.
When you don’t need to change code and want to add additional behavior simple use decorator pattern and decorate your existing code:
public class MathMeasure implements IMath < private final IMath math; private long lastMethodTime; public MathMeasure(IMath math) < this.math = math; >@Override public long add(int x, int y) < long result; long start = System.currentTimeMillis(); result = math.add(x, y); long end = System.currentTimeMillis(); lastMethodTime = end - start; return result; >@Override public long sub(int x, int y) < //same code here like in previous method >public long lastMethodInvokationTime() < return lastMethodTime; >> This is basic idea of how it works, you may need to add more complex time execution logging. Let’s see what we done here, with decorator pattern you create something that implements IMath interface and put it inside decorator after that feel free to pass this bunch to clients (another part of application) because decorator also have IMath interface and clients don’t see additional methods but you may collect data after clients IMath usage.
java how can I measure method call times?
As one of the ppl suggested it was CPUT time. I wondered whether there is any Java built-in method. Not looking for anything complex such as profiler but rather something I can use ad hoc in my code. Something like this: long startTime = System.currentTimeMillis(); tommy.move(0,0); long endTime = System.currentTimeMillis(); System.out.println(«That took » + (endTime — startTime) + » milliseconds»);//but is there a way to do it in one line with some Java method?
@aretal Your example measures elapsed (wall) time, not CPU time. Apparently it’s hard to this in one line as you need to at least mark the lines where the clock is supposed to start and stop somehow. Aspects can give you a compact solution, but it’s probably overkill to dig into AOP if all you want is to measure time.
yes I understand the limitations of my solution, that’s why hoped for a better one. It seems it is AOP. thank you anyway
4 Answers 4
Use either a profiler or count them manually:
public static int MOVE_CALL_COUNT; public void move(int, int)
Profiling is recommended. In NetBeans there is a built-in profiler. Otherwise, VisualVM is a recommended option, which is the same profiler as in NetBeans.
If you really want to know how long it takes to run these methods, use a profiler.
I think aretai means the amount of user or CPU time, as the post is tagged [time]. Also he directly asked for a generic methods, so the manual count is probably not a correct answer either. Of course, the use of a profiler is likely the way to proceed.
Try the profiler in the JDK, visualvm.
Use dedicated tools that will show You even more You need 🙂 VisualVM is best one in my opinion, However there are other available (e.g. JConsole that is provided in JDK natively, or JRockit that is paid).
Read more here on my post
These tools shows running apps and resources consumed by them along with servlets (if any) processing times, error and call counts etc. Also threads and classes instantiated are listed. This will surely satisfy Your needs
If it is testing to see how long each method takes to execute, then there are already some good questions relating to this on SO. Check out this one for example.
My preference, especially in a larger project with many methods, would be to use AOP so it doesn’t involve changing existing code too much. This answer on the question I linked to above suggests AOP for the same reasons. As he suggests, going in depth in AOP is beyond the scope of this, but it is certainly worth a look. Take a look at this tutorial into how to use spring for method timings.
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How can i benchmark method execution time in java?
I have a program which i have myself written in java, but I want to test method execution times and get timings for specific methods. I was wondering if this is possible, by maybe somehow an eclipse plug-in? or maybe inserting some code? I see, it is quite a small program, nothing more than 1500 lines, which would be better a dedicated tool or System.currentTimeMillis() ?
You should use System.nanoTime() to measure elapsed time (see stackoverflow.com/questions/238920/…), not System.currentTimeMillis() . Other points (warmup, JIT) mentioned by @Stephen in a comment are still valid.
10 Answers 10
Other than using a profiler, a simple way of getting what you want is the following:
@Stephen C — fair points. The above is the method I primarily use when trying to get a quick idea to method efficiency. My requirements in most cases aren’t needed to single ms precision.
I might want to add to this answer that you could take warmup into consideration. By using the -XX:CompileThreshold=100 flag you force the JVM to compile your method to native code when it has been executed 100 times. So you could execute it 100 times without timing. After that its has been compiled to native code and you could measure it properly.
Is there a way to compensate for the time it takes just to call the method? For example I don’t want to count the time it takes for the parameters to be copied over and the return address to be given etc.
This is one of the worst ways of measuring execution times of small pieces of code in Java because (i) does not warm-up the code, making measuerements fluctuate so much you can’t effectively measure nothing (ii) can be affected by DCE, CP and other optmizations not present in the real code (iii) the granularity of millis is extremely coarse. Check my answer for a better method.
If the bottleneck is big enough to be observed with a profiler, use a profiler.
If you need more accuracy, the best way of measuring an small piece of code is the use of a Java microbenchmark framework like OpenJDK’s JMH or Google’s Caliper. I believe they are as simple to use as JUnit and not only you will get more accurate results, but you will gain the expertise from the community to do it right.
Follows a JMH microbenchmark to measure the execution time of Math.log() :
private double x = Math.PI; @Benchmark public void myBenchmark()
Using the currentMillis() and nanoTime() for measuring has many limitations:
- They have latency (they also take time to execute) which bias your measurements.
- They have VERY limited precision, this means you can mesure things from 26ns to 26ns in linux and 300 or so in Windows has described here
- The warmup phase is not taken into consideration, making your measurements fluctuate A LOT.
The currentMillis() and nanoTime() methods in Java can be useful but must be used with EXTREME CAUTION or you can get wrong measurements errors like this where the order of the measured snippets influence the measurements or like this where the author wrongly conclude that several millions of operations where performed in less than a ms, when in fact the JMV realised no operations where made and hoisted the code, running no code at all.
Here is a wonderful video explaining how to microbenchmark the right way: https://shipilev.net/#benchmarking
For quick and dirty time measurement tests, don’t use wall-clock time ( System.currentTimeMillis() ). Prefer System.nanoTime() instead:
public static void main(String. ignored) throws InterruptedException < final long then = System.nanoTime(); TimeUnit.SECONDS.sleep(1); final long millis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - then); System.out.println("Slept for (ms): " + millis); // = something around 1000. >You should use a profiler like
They will easily integrate with any IDE and show whatever detail you need.
Of course these tools are complex and meant to be used to profile complex programs, if you need just some simple benchmarks I suggest you to use System.currentTimeMillis() or System.nanoTime() and calculate delta of millisecs between calls by yourself.
I see, it is quite a small program, nothing more than 1500 lines, which would be better a dedicated tool or System.currentTimeMillis()?
If you just need to check how fast some methods perform go with System.currentTimeMillis(), but mind that it’s not precise at all! You can have quantization of tenths of millisecs and similar issues. Profiling is far more the best way to do what you need to do but it needs a little bit of learning.
Using a profiler is better because you can find out average execution times and bottlenecks in your app.
Stopwatch stopwatch = Stopwatch.createStarted(); myFunctionCall(); LOGGER.debug("Time taken by myFunctionCall: " + stopwatch.stop()); Jprofiler and yourkit are good, but cost money.
There is a free plugin for eclispe called TPTP (Test & Performance Tools Platform) That can give you code execution times. Here is a tutorial that a quick google search brought up. http://www.eclipse.org/articles/Article-TPTP-Profiling-Tool/tptpProfilingArticle.html
Another Custom made solution could be based on the the following post : http://www.mkyong.com/spring/spring-aop-examples-advice/
You then have also the possibility to use the utilities around application monitoring & snmp. If you need to «time» your methods on a regular basis in a production environment, you proabably should consider using one of the those SNMP tools
Usually I store the time in a .txt file for analise the outcome
StopWatch sWatch = new StopWatch(); sWatch.start(); //do stuff that you want to measure downloadContent(); sWatch.stop(); //make the time pretty long timeInMilliseconds = sWatch.getTime(); long hours = TimeUnit.MILLISECONDS.toHours(timeInMilliseconds); long minutes = TimeUnit.MILLISECONDS.toMinutes(timeInMilliseconds - TimeUnit.HOURS.toMillis(hours)); long seconds = TimeUnit.MILLISECONDS.toSeconds(timeInMilliseconds - TimeUnit.HOURS.toMillis(hours) - TimeUnit.MINUTES.toMillis(minutes)); long milliseconds = timeInMilliseconds - TimeUnit.HOURS.toMillis(hours) - TimeUnit.MINUTES.toMillis(minutes) - TimeUnit.SECONDS.toMillis(seconds); String t = String.format("%02d:%02d:%02d:%d", hours, minutes, seconds, milliseconds); //each line to store in a txt file, new line String content = "Ref: " + ref + " - " + t + "\r\n"; //you may want wrap this section with a try catch File file = new File("C:\\time_log.txt"); FileWriter fw = new FileWriter(file.getAbsoluteFile(), true); //append content set to true, so it does not overwrite existing data BufferedWriter bw = new BufferedWriter(fw); bw.write(content); bw.close();