Program in JAVA to calculate age of person from birthdate and current date

Question

This code will accept from the user the current date, month, and year; and their birth date, birth month, birth year. It outputs the age of the person in years, months and days. The code as I have written it does its job. I have cross-checked with a website on the internet. I want to know:

How do I implement the Date class in Java to get the current Date, Month and Year? Will I be better off with Swing or AWT kits, if I want to make a GUI?

import java.util.*;
class AgeCalc
{
    static int[] MonthDays = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
    public static void Input(int cd, int cm, int cy)
    {
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter Birth Date");
        int bd = scan.nextShort();
        System.out.println("Enter Birth Month");
        int bm = scan.nextShort();
        System.out.println("Enter Birth Year");
        int by = scan.nextShort();
        int fnd = (DaysofMidYears(by, cy)) + Birth_CurrYearDays(bd, bm, by, cd, cm, cy);
        int y = fnd / 365;
        int m = (fnd - (y * 365)) / 30;
        int d = (fnd - (y * 365) - (m * 30));
        System.out.println("No. of Days: "+d);
        System.out.println("No. of Months: "+m);
        System.out.println("No. of Years: "+y);
    }
    public static boolean LeapYearTest(int y)
    {
        boolean lys = 
        ( ((y % 400) == 0) ? true 
        : ((y % 10) == 0) ? false 
        : ((y % 4) == 0) ? true 
        : false );
        return lys;
    }
    public static int DaysofMidYears(int by, int cy)
    {
        int dmy = 0;
        for
        (int i = (by + 1); i <= (cy - 1); i++)
        {
            dmy += 365;
            if 
            ((LeapYearTest(i)) == true)
            {
                dmy += 1;
            }
        }
        return dmy;
    }
    public static int InitialDaysofYear(int d, int m, int y)
    {
        int id = d;
        for
        (int i = 1; i <= (m - 1); i++)
        {
            id += (MonthDays[i - 1]);
        }
        if
        (((LeapYearTest(y)) == true) && (m > 2))
        {
            id += 1;
        }
        return id;
    }
    public static int Birth_CurrYearDays(int bd, int bm, int by, int cd, int cm, int cy)
    {
        int bcyd = 0;
        bcyd += (InitialDaysofYear(cd, cm, cy));
        bcyd += (365 - (InitialDaysofYear(bd, bm, by)));
        if
        ((LeapYearTest(by)) == true)
        {
            bcyd += 1;
        }
        return bcyd;
    }
}

_How do I implement the Date class in Java to get the current Date, Month and Year?_ Do you need to write your own implementation of class `java.util.Date`? — Abra, Dec 07 '19 at 05:52
_How do I make it a GUI?_ You need to write a GUI in java? If yes, then you have either [Swing](https://docs.oracle.com/javase/tutorial/uiswing/index.html) or [JavaFX](https://docs.oracle.com/javase/8/javafx/get-started-tutorial/jfx-overview.htm). — Abra, Dec 07 '19 at 05:54
Welcome to Stack Overflow. How to make a GUI is way too broad for a Stack Overflow question. Fortunately there are already numerous tutorials on that subject out there. Use your search engine. — Ole V.V., Dec 07 '19 at 11:32
This looks like a typo: `(y % 10) == 0`. Should it be `y % 100`? And such a typo illustrates quite well why it’s better to use a proven standard library than to write your own logic for the task. — Ole V.V., Dec 07 '19 at 11:33
Does this answer your question? [How do I calculate someone's age in Java?](https://stackoverflow.com/questions/1116123/how-do-i-calculate-someones-age-in-java) If not, search for other existing questions that do. There most likely are more than one. — Ole V.V., Dec 07 '19 at 11:35

score 3 · Answer 1 · edited Dec 07 '19 at 12:05

We no longer use the java.util.Date or java.sql.Date classes. They were supplanted years ago by the modern java.time classes defined in JSR 310.

For a date-only value without time-of-day and without time zone, use LocalDate.

LocalDate birthDate = LocalDate.of(y, m, d);

For elapsed time, or age, use Period class.

LocalDate today = LocalDate.now();
Period age = Period.between(birthDate, today);
long years = age.getYears();

ttarczynski · Accepted Answer · 2019-12-07T12:24:00.147

Time calculations are tricky beasts, and it's best to avoid implementing custom Date/Time classes (except maybe for exercise or learning purposes). As for your question, use Java 8's java.time.* classes:

ZoneId timeZoneId = ZoneId.of("Europe/Warsaw"); // assuming you're in Poland - put the your time zone name here ;-)
LocalDate today = LocalDate.now(timeZoneId);
LocalDate birthday = LocalDate.of(year, month, day);
Period lifePeriod = Period.between(birthday, today);
long age = lifePeriod.getYears();

As for the GUI part of your question - it's "a bit" too broad :-) As a general advice - learn about JavaFX, and how to build UIs in it, if you want to use Java as your toolkit for GUI apps.

EDIT: Side note on codestyle and conventions - Java has a well established method and variable naming conventions - it's always a good practice to learn and use them. It makes your code more readable for those familliar with the conventions.

Program in JAVA to calculate age of person from birthdate and current date

2 Answers2