Java LocalDateTime plusDays()

In this guide, you will learn about the LocalDateTime plusDays() method in Java programming and how to use it with an example.

1. LocalDateTime plusDays() Method Overview

Definition:

The LocalDateTime.plusDays() method returns a copy of the LocalDateTime with the specified number of days added.

Syntax:

LocalDateTime plusDays(long days)

Parameters:

- days: The number of days to add, may be negative.

Key Points:

- The LocalDateTime.plusDays() method is useful for date arithmetic where you want to manipulate the day part of a LocalDateTime.

- The returned LocalDateTime instance is immutable, which means the original LocalDateTime instance remains unchanged.

- The method takes care of month and year boundaries. For example, adding 1 day to the last day of a month will return the first day of the next month.

- If adding the days results in an overflow of the maximum date (LocalDateTime.MAX), a DateTimeException will be thrown.

2. LocalDateTime plusDays() Method Example

import java.time.LocalDateTime;

public class LocalDateTimePlusDaysExample {
    public static void main(String[] args) {
        LocalDateTime dateTime = LocalDateTime.of(2023, 12, 31, 16, 30);

        // Add 1 day to the LocalDateTime
        LocalDateTime result1 = dateTime.plusDays(1);

        // Subtract 5 days from the LocalDateTime
        LocalDateTime result2 = dateTime.plusDays(-5);

        System.out.println("Original DateTime: " + dateTime);
        System.out.println("After adding 1 day: " + result1);
        System.out.println("After subtracting 5 days: " + result2);
    }
}

Output:

Original DateTime: 2023-12-31T16:30
After adding 1 day: 2024-01-01T16:30
After subtracting 5 days: 2023-12-26T16:30

Explanation:

In the example, we have a LocalDateTime set to December 31, 2023.

- When we add 1 day using plusDays(1), the date becomes January 1, 2024, which demonstrates the method's capability to handle month and year boundaries.

- When we subtract 5 days using plusDays(-5), the date becomes December 26, 2023.