How to calculate elapsed / execute time in Java

How to calculate elapsed / execute time in Java
In Java, you can use the following ways to measure elapsed time in Java.

1. System.nanoTime()
This is the recommended solution to measure elapsed time in Java.

ExecutionTime1.java
package com.mkyong.time;

import java.util.concurrent.TimeUnit;

public class ExecutionTime1 {

public static void main(String[] args) throws InterruptedException {

//start
long lStartTime = System.nanoTime();

//task
calculation();

//end
long lEndTime = System.nanoTime();

//time elapsed
long output = lEndTime - lStartTime;

System.out.println("Elapsed time in milliseconds: " + output / 1000000);

}

private static void calculation() throws InterruptedException {

//Sleep 2 seconds
TimeUnit.SECONDS.sleep(2);

}
}

Output may vary.

2004

2. System.currentTimeMillis()
ExecutionTime2.java
package com.mkyong.time;

import java.util.concurrent.TimeUnit;

public class ExecutionTime2 {

public static void main(String[] args) throws InterruptedException {

long lStartTime = System.currentTimeMillis();

calculation();

long lEndTime = System.currentTimeMillis();

long output = lEndTime - lStartTime;

System.out.println("Elapsed time in milliseconds: " + output);

}

private static void calculation() throws InterruptedException {

//Sleep 2 seconds
TimeUnit.SECONDS.sleep(2);

}
}

Output may vary.

2006

3. Instant.now().toEpochMilli()
In Java 8, you can try the new java.time.Instant

ExecutionTime3.java
package com.mkyong.time;

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

public class ExecutionTime3 {

public static void main(String[] args) throws InterruptedException {

long lStartTime = Instant.now().toEpochMilli();

calculation();

long lEndTime = Instant.now().toEpochMilli();

long output = lEndTime - lStartTime;

System.out.println("Elapsed time in milliseconds: " + output);

}

private static void calculation() throws InterruptedException {

//Sleep 2 seconds
TimeUnit.SECONDS.sleep(2);

}
}

Output may vary.

2006

4. Date().getTime()
ExecutionTime4.java
package com.mkyong.time;

import java.util.Date;
import java.util.concurrent.TimeUnit;

public class ExecutionTime4 {

public static void main(String[] args) throws InterruptedException {

long lStartTime = new Date().getTime();

calculation();

long lEndTime = new Date().getTime();

long output = lEndTime - lStartTime;

System.out.println("Elapsed time in milliseconds: " + output);

}

private static void calculation() throws InterruptedException {

//Sleep 2 seconds
TimeUnit.SECONDS.sleep(2);

}
}

Output may vary.

2007

http://www.mkyong.com/java/how-do-calculate-elapsed-execute-time-in-java/
http://www.mkyong.com/tutorials/java-date-time-tutorials/