Java 8 – Calculate Age from Birthdate

Introduction

With the introduction of the java.time package in Java 8, handling dates and times in Java has become more intuitive and powerful. One common task is calculating a person’s age based on their birthdate. This is often required in applications involving user profiles, forms, or any system that tracks personal information.

In this guide, we’ll explore how to calculate the age from a given birthdate using Java 8’s java.time package.

Table of Contents

• Problem Statement
• Solution Steps
• Java Program
  • Calculate Age from Birthdate
• Advanced Considerations
• Conclusion

Problem Statement

The task is to create a Java program that:

• Takes a birthdate as input.
• Calculates the person’s age based on the current date.

Example:

• Input: A LocalDate object representing 1990-08-28.
• Output: An integer representing the person’s age, such as 34 (assuming the current date is 2024-08-28).

Solution Steps

1. Create a LocalDate Object for the Birthdate: Represent the birthdate of the person.
2. Get the Current Date: Use the LocalDate.now() method to retrieve the current date.
3. Calculate the Age: Use the Period.between() method to calculate the difference between the birthdate and the current date.
4. Handle the Result: The result is the person’s age, which you can use as needed in your application.

Java Program

Calculate Age from Birthdate

The following example demonstrates how to calculate age from a birthdate in Java 8.

import java.time.LocalDate;
import java.time.Period;

/**
 * Java 8 - Calculate Age from Birthdate
 * Author: https://www.rameshfadatare.com/
 */
public class AgeCalculator {

    public static void main(String[] args) {
        // Step 1: Create a LocalDate object for the birthdate
        LocalDate birthDate = LocalDate.of(1990, 8, 28);

        // Step 2: Get the current date
        LocalDate currentDate = LocalDate.now();

        // Step 3: Calculate the age
        int age = Period.between(birthDate, currentDate).getYears();

        // Step 4: Display the age
        System.out.println("Age: " + age);
    }
}

Output

Age: 34

Explanation

• LocalDate.of(1990, 8, 28) creates a LocalDate instance for the specified birthdate.
• LocalDate.now() retrieves the current date.
• Period.between(birthDate, currentDate).getYears() calculates the number of years between the birthdate and the current date, which represents the age.
• The resulting age is printed, showing the number of years.

Advanced Considerations

• Handling Future Birthdates: If the birthdate is in the future, the Period.between() method will return a negative age. You might want to add validation to ensure the birthdate is not in the future.

• Time Zones: The LocalDate.now() method uses the system’s default time zone. If your application runs in different time zones, ensure consistency by specifying the time zone explicitly if necessary.

• Leap Years: The Period.between() method correctly handles leap years, ensuring accurate age calculation even for individuals born on February 29.

• Day Calculation: If you need to calculate the exact age, including months and days, you can use Period.getMonths() and Period.getDays() in addition to getYears().

Conclusion

This guide covers the calculation of age from a birthdate using Java 8’s java.time package. The Period.between() method provides a simple and effective way to calculate the difference between two dates, making it easy to determine a person’s age. Whether you’re building user profiles, processing forms, or managing any system involving dates, calculating age is a common requirement that Java 8 handles with ease.