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.favtuts.time;

import java.util.concurrent.TimeUnit;

public class ElapsedTimeExecutionTime {

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

    static void measuredElapsedTimeWithSystemNanoTime() 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.

Elapsed time in milliseconds: 2000

2. System.currentTimeMillis()

ExecutionTime2.java

package com.favtuts.time;

import java.util.concurrent.TimeUnit;

public class ElapsedTimeExecutionTime {

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

    static void measuredElapsedTimeWithSystemCurrentTimeMillis() 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.

Elapsed time in milliseconds: 2000

3. Instant.now().toEpochMilli()

In Java 8, you can try the new java.time.Instant

ExecutionTime3.java

package com.favtuts.time;

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

public class ElapsedTimeExecutionTime {

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

    static void measuredElapsedTimeWithInstantNowToEpochMilli() 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.

Elapsed time in milliseconds: 2000

4. Date().getTime()

ExecutionTime4.java

package com.favtuts.time;

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

public class ElapsedTimeExecutionTime {

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

Elapsed time in milliseconds: 2001

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-basic/time

References

1. Stackoverflow – Is System.nanoTime() completely useless?
2. Stackoverflow – System.currentTimeMillis vs System.nanoTime
3. System#nanoTime JavaDoc
4. Instant#toEpochMilli JavaDoc