My first TWiki page, A Simple Age Calculator Class.

Sometimes you need to calculate an Age of the person knowing it's birthday.

It seems like a trivial task, but many beginners trying to reinvent the wheel while doing it.

Tip A simple search on java.sun.com forums gives you an idea what some developers doing a simple search (will open in this window)

To show that age calculation should not be such a pain, I put together a small class that calculates your age based on given birthday.

import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.text.SimpleDateFormat;
import java.text.ParseException;

/**
 * User: IvanLatysh@yahoo.ca
 * Date: 27-May-2004
 * Time: 6:57:04 PM
 */

public class Age {

  public Age(long birthday) {
    Calendar age = Calendar.getInstance(Locale.getDefault());
    age.setTimeInMillis(Math.abs(birthday-System.currentTimeMillis()));
    System.out.println("Your are "+(age.get(Calendar.YEAR)-1970)+" years, "+age.get(Calendar.MONTH)+" month, "+age.get(Calendar.DAY_OF_MONTH)+" days "+(System.currentTimeMillis()-birthday<0 ?"Not Born Yet" :"Old")+".");
  }

  public static void main(String[] args) {
    SimpleDateFormat dateFormatter = new SimpleDateFormat("dd/MM/yyyy");
    if (args.length==0) {
      System.out.println("Usage:\n java Age dd/mm/yyyy\nWhere:\n dd - date\n mm - month\n yyyy - year");
    } else {
      try {
        final Date birthday = dateFormatter.parse(args[0]);
        System.out.println("Your birthday is " + dateFormatter.format(birthday));
        final Age myAge = new Age(birthday.getTime());
      } catch (ParseException e) {
        System.out.println("Error parsing your birthday.");
        e.printStackTrace();
      }
    }
  }

}

How to use it:

• Copy the code from this page into the new file Age.java
• Compile it

  C:\> javac Age.java

• Run it

  C:\> java Age 10/10/2004

• Have fun.

-- Main.ivanlatysh - 28 May 2004