How Can I Accurately Calculate Age in Java Using the Modern Date and Time API?

Calculating Age in Java: A Revised Approach

In Java, obtaining an age requires a precise method. The deprecated method of using the getYear() function has prompted the search for a more current solution.

To tackle this, the introduction of Java Date and Time API (JSR-310) in JDK 8 simplifies the process. Consider the following method:

public int getAge() {
    LocalDate today = LocalDate.now();
    long ageInMillis = today.toEpochDay() - birthDate.toEpochDay();
    return (int) TimeUnit.MILLISECONDS.toDays(ageInMillis) / 365;
}

Explanation:

• It utilizes the toEpochDay() method to convert both the current date (obtained through LocalDate.now()) and the birth date to long-form epoch day representations.
• The difference between these epoch days in milliseconds is obtained using simple arithmetic.
• To convert the age in milliseconds to years, it's divided by the number of milliseconds per year (365 days).

Unit Testing:

@Test
public void getAge_Success() {
    Person person = new Person(LocalDate.parse("1970-01-01"), "Jane Doe");
    assertEquals(50, person.getAge());
}

Conclusion:

By embracing the Java Date and Time API, age calculation becomes both accurate and efficient. The revised approach provides a robust solution that seamlessly fits into modern Java development.

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