How to find time taken to run a Java program?

Question

I have a Java application that I've been working on and I just realized that the program has to return a value in less than a minute, but don't know how to find or display the time taken to run the program. How to find time taken to run a program?

I am sorry but your question is not clear enough. I think that eclipse is irrelevant here. Runtime is irrelevant too because it is confusing. JDK has class Runtime and you can get its singleton instance by invoking Runtime.getRuntime() but it seems not what you are looking for. Please try to re-think your question and re-write it. — AlexR, Jul 11 '11 at 06:36

score 80 · Accepted Answer · edited May 14 '19 at 01:49

80

You can compare times using System.nanoTime() . It will return the time in nanoseconds.

Returns the current value of the most precise available system timer, in nanoseconds.

You could use it like this:

long startTime = System.nanoTime();

// code

long endTime = System.nanoTime();
System.out.println("Took "+(endTime - startTime) + " ns");

Usefull links:

System.nanoTime()

edited May 14 '19 at 01:49

Kerwin Sneijders

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answered Jul 11 '11 at 06:34

jmj

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score 15 · Answer 2 · answered Jul 11 '11 at 06:35

There is no built-in way to see for how long your program has been running. However, you could at the start of the program just store the current time, so that sometime later you can see how much time has elapsed.

public class MyProgram {
    private static long startTime = System.currentTimeMillis();

    public static void main(String[] args) {
        // Do stuff...

        // At the end
        long endTime = System.currentTimeMillis();
        System.out.println("It took " + (endTime - startTime) + " milliseconds");
    }
}

score 3 · Answer 3 · edited May 13 '19 at 22:43

If you have Spring as a dependency of your project (or don't mind adding it), you can use StopWatch. As the name suggests, once initialized it will count the time until you stop it. You can then check the time taken for a task. Multiple StopWatches can be used simultaneously to multiple tasks keeping the code clean.

Besides keeping your code clean, StopWatches help with formatting the time and other utility methods.

public void myMethod(){
    StopWatch stopWatch = new StopWatch();

    stopWatch.start("Task1");
    // ...
    // Do my thing
    // ...
    stopWatch.stop();
    System.out.println("Task executed in " + stopWatch.getTotalTimeSeconds() + "s");
}

score 2 · Answer 4 · answered Jun 27 '18 at 10:17

You can use 2 APIs provided by System class

System.currentTimeMillis() If code takes time in Millisecond range
System.nanoTime() If code takes time in Nanosecond range

Sample Code

public class TestTimeTaken {
    public static void main(String args[]) throws InterruptedException{
        long startTimeNanoSecond = System.nanoTime();
        long startTimeMilliSecond = System.currentTimeMillis();

        //code
        Thread.sleep(1000);
        //code

        long endTimeNanoSecond = System.nanoTime();
        long endTimeMilliSecond = System.currentTimeMillis();

        System.out.println("Time Taken in "+(endTimeNanoSecond - startTimeNanoSecond) + " ns");
        System.out.println("Time Taken in "+(endTimeMilliSecond - startTimeMilliSecond) + " ms");


    }
}

score 1 · Answer 5 · answered May 13 '19 at 19:32

I like using the Apache Commons StopWatch class when I have the library available.

import org.apache.commons.lang3.time.StopWatch;

// ...

StopWatch stopWatch = new StopWatch();
String message = "Task : %s (%s) seconds";

// ...

stopWatch.split();
System.out.println(String.format(message, "10", stopWatch.toSplitString()));

// ...

stopWatch.split();
System.out.println(String.format(message, "20", stopWatch.toSplitString()));

stopWatch.stop();

score 1 · Answer 6 · answered Jul 11 '11 at 06:37

1

If you just want to know how long does your program run use System.currentTimeMillis() in the beginning and end of your program.

answered Jul 11 '11 at 06:37

AlexR

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score 0 · Answer 7 · answered Jul 11 '11 at 08:08

This is a typical usecase for aspects, for example using Spring AOP:

@Aspect
public class TimerAspect {

    private static final Logger LOG = Logger.getLogger(TimerAspect.class);

    @Around("com.xyz.myapp.MyClass.myMethod()")
    public Object doBasicProfiling(ProceedingJoinPoint pjp) throws Throwable {
        long startTime = System.nanoTime();
        Object retVal = pjp.proceed();
        long endTime = System.nanoTime();
        LOG.info(String.format("Call to %s.%s with args %s took %s ns", pjp.getTarget(), pjp.getSignature(), Arrays.toString(pjp.getArgs()), endTime - startTime));
        return retVal;
    }
}

And in your application context:

<aop:aspectj-autoproxy/>
<bean id="myAspect" class="org.xyz.TimerAspect"/>

How to find time taken to run a Java program?

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