Measuring Execution Time of a Method in Java

Old fashioned Way

System.currentTimeMillis()

Accuracy is only in milli seconds, so if you are timing a method which is quite small then you might not get good results.

List<Integer> input = getInputList();

long t1 = System.currentTimeMillis();

Collections.sort(input);

long t2 = System.currentTimeMillis();

System.out.println("Time Taken ="+ (t2-t1) + " in milli seconds");

Using Nano seconds

System.nanoTime()

Preferred approach (compared to first one). But do keep in mind that not all systems will provide accuracy in nano time.

List<Integer> input = getInputList();

long t1 = System.nanoTime();

Collections.sort(input);

long t2 = System.nanoTime();

System.out.println("Time Taken ="+ (t2-t1) + " in nano seconds");

Java 8

List<Integer> input = getInputList();

Instant start = Instant.now();

Collections.sort(input);

Instant end = Instant.now();

System.out.println("Time Taken ="+ Duration.between(start, end) + " in nano seconds");

Guava

Stopwatch stopwatch = new Stopwatch().start();

Collections.sort(input);

stopwatch.stop();