How do I use atTime() method of Java Date-Time API?

The atTime() method belongs to the LocalDate class in the Java Date-Time API, not the Date class. This method combines this date with a time to create a LocalDateTime.

Here’s an example:

package org.kodejava.datetime;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;

public class AtTimeExample {
    public static void main(String[] args) {
        // Create a LocalDate instance
        LocalDate date = LocalDate.of(2023, 1, 23);

        // Create a LocalTime instance
        // 24-hour clocks
        LocalTime time = LocalTime.of(13, 45);

        // Use atTime() to combine date and time into a LocalDateTime
        LocalDateTime dateTime = date.atTime(time);

        System.out.println(dateTime);
    }
}

Output:

2023-01-23T13:45

In this example, a LocalDate and a LocalTime are combined into a LocalDateTime using the atTime() method.

The LocalDate class also has an overloaded atTime method that takes the hour and minute directly, instead of a LocalTime instance.

Here’s an example where we set 14 hours and 30 minutes directly.

package org.kodejava.datetime;

import java.time.LocalDate;
import java.time.LocalDateTime;

public class AtTimeOtherExample {
    public static void main(String[] args) {
        // Create a LocalDate instance
        LocalDate date = LocalDate.of(2023, 1, 23);

        // Use atTime() to combine date and hour and minute into a
        // LocalDateTime
        LocalDateTime dateTime = date.atTime(14, 30);

        System.out.println(dateTime);
    }
}

Output:

2023-01-23T14:30

In this example, 14:30 (in 24-hour clock) is directly passed into atTime. There is another version of atTime() that takes hrs, min, and sec. That would look like this:

// include seconds
LocalDateTime dateTime = date.atTime(14, 30, 20);

// include nano seconds
LocalDateTime dateTime = date.atTime(14, 30, 20, 200);

These are all the overloaded versions of atTime() in LocalDate.

Remember, LocalDate, LocalTime, LocalDateTime and others from Java Date-Time API are designed to replace the old Date and Calendar classes from java.util package. They are more consistent, easier to understand and use.

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Wayan

Founder at Kode Java

A programmer, runner and recreational diver, lives on the island of Bali, Indonesia. Programming in Java, Spring Framework, Hibernate / JPA, MySQL. To support me working on this project, buy me a cup of coffee, every little bit helps. Thank you.

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