[Java] How to measure execution time ?

1. Measure time with System.nanoTime and System.currentTimeMillis

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package javautility; import java.io.IOException; import java.util.concurrent.TimeUnit; public class JavaUtility { static void testTimeMeasureNano() throws InterruptedException { long start = System.nanoTime(); Thread.sleep(1200); long end = System.nanoTime(); long diff = end - start; System.out.println("Elapsed: " + diff + " nsec, " + TimeUnit.NANOSECONDS.toMillis(diff) + " msec" ); } static void testTimeMeasureMillis() throws InterruptedException { long start = System.currentTimeMillis(); Thread.sleep(1200); long end = System.currentTimeMillis(); long diff = end - start; System.out.println("Elapsed: " + diff + " msec"); } public static void main(String[] args) throws IOException, InterruptedException { testTimeMeasureNano(); System.out.println("----------"); testTimeMeasureMillis(); } }

Result:

Elapsed: 1199611928 nsec, 1199 msec
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Elapsed: 1201 msec

2. Measure time with LocalTime

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package javautility; import java.io.IOException; import java.time.Duration; import java.time.LocalTime; import java.util.concurrent.TimeUnit; public class JavaUtility { static void timeMeasureLocalTime() throws InterruptedException { LocalTime start = LocalTime.now(); Thread.sleep(1200); LocalTime end = LocalTime.now(); Duration diff = Duration.between(start,end); System.out.println("Elapsed: " + diff.toNanos() + " nsec, " + TimeUnit.NANOSECONDS.toMillis(diff.toNanos()) + " msec" ); } public static void main(String[] args) throws IOException, InterruptedException { timeMeasureLocalTime(); } }

Result:

Elapsed: 1201000000 nsec, 1201 msec