How to calculate execution / elapsed time Java 8?

package com.java2novice.datetime;

import java.time.Instant;
import java.util.concurrent.TimeUnit;

public class CalcElapsedTimeEx {

	public static void main(String a[]) {

		// calculate elapsed time in milli seconds
		Long startTime = Instant.now().toEpochMilli();
		try {
			// do your business logic here
			doYourBusinessLogic();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		Long endTime = Instant.now().toEpochMilli();
		Long elapsedTime = endTime - startTime;
		System.out.println("Elapsed time in milli seconds: "+elapsedTime);

		// calculate elapsed time in seconds
		Long stTimeInSec = Instant.now().getEpochSecond();
		try {
			// do your business logic here
			doYourBusinessLogic();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		Long endTimeInSec = Instant.now().getEpochSecond();

		elapsedTime = endTimeInSec - stTimeInSec;
		System.out.println("Elapsed time in seconds: "+elapsedTime);
	}

	private static void doYourBusinessLogic() throws InterruptedException {

		TimeUnit.SECONDS.sleep(3);
	}
}

Elapsed time in milli seconds: 3004
Elapsed time in seconds: 3