How Can I Reliably Calculate Age in Years Using Java?

Java Method for Calculating Age

Problem:

Develop a Java method that returns an age in years as an integer. The method takes a Date object representing the birth date.

Current Implementation:

public int getAge() {
    long ageInMillis = new Date().getTime() - getBirthDate().getTime();

    Date age = new Date(ageInMillis);

    return age.getYear();
}

Limitations:

• getYear() method is deprecated.
• The accuracy of the current method is questionable without unit tests.

Improved Solution with JDK 8:

JDK 8 introduces a refined solution using the LocalDate class:

public class AgeCalculator {

    public static int calculateAge(LocalDate birthDate, LocalDate currentDate) {
        if ((birthDate != null) & (currentDate != null)) {
            return Period.between(birthDate, currentDate).getYears();
        } else {
            return 0;
        }
    }
}

JUnit Test:

public class AgeCalculatorTest {

    @Test
    public void testCalculateAge_Success() {
        // setup
        LocalDate birthDate = LocalDate.of(1961, 5, 17);
        // exercise
        int actual = AgeCalculator.calculateAge(birthDate, LocalDate.of(2016, 7, 12));
        // assert
        Assert.assertEquals(55, actual);
    }
}

Recommendation:

Upgrade to JDK 8 for an improved and reliable solution for calculating age.

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