Measure execution time for a Java method [duplicate]

Question

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

Answer 1

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)); 

Answer 2

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.

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From "Java Platform Performance: Strategies and Tactics" book:

With System.currentTimeMillis()

class TimeTest1 {    public static void main(String[] args) {        long startTime = System.currentTimeMillis();        long total = 0;       for (int i = 0; i < 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 < 10000000; i++) {          total += i;       }        timer.stop();       System.out.println(timer.getElapsedTime());    } } 

See here (archived).

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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.