Java 8 – How to Get the Current Time in Milliseconds

Introduction

Java 8 introduced the java.time package, which provides a modern and comprehensive framework for handling date and time. However, there are still many scenarios where you need to get the current time in milliseconds, such as when measuring elapsed time or interacting with systems that use timestamps. Java provides several ways to get the current time in milliseconds, both with the new java.time package and with legacy methods.

In this guide, we’ll explore how to get the current time in milliseconds using both the modern java.time API and the legacy System class.

Table of Contents

• Problem Statement
• Solution Steps
• Java Program
  • Get the Current Time in Milliseconds Using System.currentTimeMillis()
  • Get the Current Time in Milliseconds Using Instant.now()
• Advanced Considerations
• Conclusion

Problem Statement

The task is to create a Java program that:

• Retrieves the current time in milliseconds.

Example:

• Output: A long value representing the current time in milliseconds since the Unix epoch (January 1, 1970, 00:00:00 GMT).

Solution Steps

1. Use System.currentTimeMillis(): This is the traditional method to get the current time in milliseconds.
2. Use Instant.now(): This method from the java.time package can also be used to get the current time in milliseconds.

Java Program

Get the Current Time in Milliseconds Using System.currentTimeMillis()

The simplest and most direct way to get the current time in milliseconds is to use the System.currentTimeMillis() method.

/**
 * Java 8 - Get the Current Time in Milliseconds using System.currentTimeMillis()
 * Author: https://www.rameshfadatare.com/
 */
public class CurrentTimeMillisExample {

    public static void main(String[] args) {
        // Get the current time in milliseconds
        long currentTimeMillis = System.currentTimeMillis();

        // Display the current time in milliseconds
        System.out.println("Current time in milliseconds: " + currentTimeMillis);
    }
}

Output

Current time in milliseconds: 1693239045123

Get the Current Time in Milliseconds Using Instant.now()

Java 8’s java.time.Instant class provides another way to get the current time in milliseconds.

import java.time.Instant;

/**
 * Java 8 - Get the Current Time in Milliseconds using Instant.now()
 * Author: https://www.rameshfadatare.com/
 */
public class CurrentTimeMillisUsingInstant {

    public static void main(String[] args) {
        // Get the current time in milliseconds using Instant
        long currentTimeMillis = Instant.now().toEpochMilli();

        // Display the current time in milliseconds
        System.out.println("Current time in milliseconds: " + currentTimeMillis);
    }
}

Output

Current time in milliseconds: 1693239045123

Explanation

• System.currentTimeMillis(): This method returns the current time in milliseconds since the Unix epoch. It’s a simple and direct approach and has been in use since the early versions of Java.
• Instant.now().toEpochMilli(): This method uses the Instant class, which represents a point in time. The toEpochMilli() method converts the Instant to milliseconds since the Unix epoch. This is part of the new date and time API introduced in Java 8.

Advanced Considerations

• Precision: While both methods provide the time in milliseconds, the Instant class supports nanosecond precision internally. However, when you call toEpochMilli(), the result is truncated to milliseconds.

• Time Zones: The milliseconds returned by both methods are relative to UTC (Coordinated Universal Time), making them suitable for time-sensitive operations like logging or measuring elapsed time.

• Performance: System.currentTimeMillis() is a native call and is generally very fast. The Instant.now() approach, while also efficient, involves more steps under the hood, but it provides more flexibility within the java.time API.

Conclusion

This guide covers how to get the current time in milliseconds using both the traditional System.currentTimeMillis() method and the modern Instant.now().toEpochMilli() method from Java 8’s java.time package. Depending on your use case, you can choose the method that best fits your needs, whether you need simplicity or are working within the broader context of the java.time API. Both methods are effective and provide accurate millisecond precision for your Java applications.