Java 8: Difference between two LocalDateTime in multiple units

Difference Between Two LocalDateTime

Java 8 introduced a powerful Date and Time API that provides developers with better control over date and time operations. One common requirement is to calculate the difference between two LocalDateTime objects in various units such as days, hours, minutes, and seconds.

This article explains how to achieve this using Java 8's Duration and ChronoUnit classes.

Understanding LocalDateTime

LocalDateTime is a class in Java 8 that represents a date-time without a time-zone. It is often used in applications where the time zone is not needed. Calculating differences between two LocalDateTime instances is straightforward with the new API.

Using the Duration Class

The Duration class measures time in seconds and nanoseconds. You can use it to calculate the difference between two LocalDateTime objects in multiple units. Here's an example:

import java.time.LocalDateTime;
import java.time.Duration;
public class Main {
   public static void main(String[] args) {
      LocalDateTime start = LocalDateTime.of(2023, 12, 1, 10, 0);
      LocalDateTime end = LocalDateTime.of(2023, 12, 2, 15, 30);      
      Duration duration = Duration.between(start, end);
      
      System.out.println("Days: " + duration.toDays());
      System.out.println("Hours: " + duration.toHours());
      System.out.println("Minutes: " + duration.toMinutes());
      System.out.println("Seconds: " + duration.getSeconds());
   }
}

Following is the output of the above code

Days: 1
Hours: 29
Minutes: 1770
Seconds: 106200

Using the ChronoUnit Enum

The ChronoUnit enum provides another way to calculate differences. It is more versatile as it supports units like weeks, months, and years:

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

public class Main {
   public static void main(String[] args) {
      LocalDateTime start = LocalDateTime.of(2023, 12, 1, 10, 0);
      LocalDateTime end = LocalDateTime.of(2023, 12, 2, 15, 30);
      
      System.out.println("Days: " + ChronoUnit.DAYS.between(start, end));
      System.out.println("Hours: " + ChronoUnit.HOURS.between(start, end));
      System.out.println("Minutes: " + ChronoUnit.MINUTES.between(start, end));
      System.out.println("Seconds: " + ChronoUnit.SECONDS.between(start, end));
   }
}

Following is the output of the above code

Days: 1
Hours: 29
Minutes: 1770
Seconds: 106200

Duration Vs ChronoUnit

Following are the differences between Duration and ChronoUnit

Conclusion

Both Duration and ChronoUnit offer effective ways to calculate differences between two LocalDateTime instances. Choose Duration for precise short-duration measurements and ChronoUnit for a broader range of units. By leveraging these tools, you can handle complex date-time calculations with ease.