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1. See how to find your Age on other Planets

AgeApplet.java

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.util.Date;
import java.util.GregorianCalendar;


/**
 * Class AgeApplet - Finds age in days
 * and converts age to age on different planets
 * 
 * @author Chris Thiel
 * @version 1.0
 */

public class AgeApplet extends Applet
{
	static final int FIRST_YEAR=1930;
	static final int LAST_YEAR=2010;
	private GregorianCalendar now, bd;
	private Label today,daysAge;
	private Choice month, day, year;
	private PlanetChoice planet;
	private Label age;
	public void init()
	{
		now=new GregorianCalendar();
		now.setTime(new Date());
		today=new Label("Today is "+showDate(now));
		Panel p=new Panel(new GridLayout(0,1));
		p.add(today);
		p.add(new Label("Enter your birth date:"));
		bd=new GregorianCalendar();
		bd.setTime(new Date());
		daysAge=new Label("You are "+daysBetween(now.getTime(),bd.getTime())+" days old");
		month=new Choice();
		month.addItem("Jan");
		month.addItem("Feb");
		month.addItem("Mar");
		month.addItem("Apr");
		month.addItem("May");
		month.addItem("Jun");
		month.addItem("Jul");
		month.addItem("Aug");
		month.addItem("Sep");
		month.addItem("Oct");
		month.addItem("Nov");
		month.addItem("Dec");
		month.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ev) 
            {
                repaint();
            }
            });
		Panel d = new Panel(new GridLayout(1,0));

		d.add(month);
		day=new Choice();
		for (int i=1;i<32;i++)
			day.addItem(" "+i);
		day.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ev) 
            {
                repaint();
            }
            });
		d.add(day);
		year = new Choice();
		for (int i=FIRST_YEAR;i<=LAST_YEAR;i++)
			year.addItem(" "+i);
		year.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ev) 
            {
                repaint();
            }
            });
		d.add(year);
		p.add(d);
		year.select(LAST_YEAR-FIRST_YEAR);
		p.add(daysAge);
		planet = new PlanetChoice();
		planet.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ev) 
            {
                repaint();
            }
            });

		double x=daysBetween(now.getTime(),bd.getTime());
		age=new Label("that's "+planet.getAge(x)+" years on ");
		p.add(age);
		p.add(planet);
		add(p);
	}
	public void paint(Graphics g)
	{
		int m=month.getSelectedIndex();
		int d=day.getSelectedIndex()+1;
		int y=year.getSelectedIndex()+FIRST_YEAR;
		bd=new GregorianCalendar(y,m,d);
		double x=daysBetween(now.getTime(),bd.getTime());
		daysAge.setText("You are "+x+" days old");		
		age.setText("that's "+planet.getAge(x)+" years on ");

	}

	public static String showDate(GregorianCalendar d)
	{
		return (d.get(d.MONTH)+1)+"/"+d.get(d.DAY_OF_MONTH)+"/"+d.get(d.YEAR);
	}
	private static long daysBetween(Date time1, Date time2) {
		final long ONE_HOUR = 60 * 60 * 1000L;
		return  (time1.getTime() - time2.getTime() + ONE_HOUR) / 
                (ONE_HOUR * 24);
	}
}

PlanetChoice.java

import java.awt.Choice;
import java.util.ArrayList;
public class PlanetChoice extends Choice
{
	private ArrayList<Double> values;
	public PlanetChoice()
	{
		super();
		values = new ArrayList<Double>();
		addItem("Mercury",87.97);
		addItem("Venus",224.7);
		addItem("Earth",365.24);
		addItem("Mars",686.93);
		addItem("Ceres",1680.5); //4.6 years
		addItem("Jupiter",4330.6);
		addItem("Saturn",10755.7);
		addItem("Uranus",30687.2);
		addItem("Neptune",60190.0);
		addItem("Pluto",90553.0);
		addItem("Varuna",103440.6); 
		addItem("Haumea",103468.0);//283.28 years
		addItem("Quaoar",105196.3);
		addItem("Makemake",113183.0);//309.88 years
		addItem("Eris(Xena)",203600.0);//557 years		
		addItem("Sedna",4404480.0);


	}
	public void addItem(String name, double daysPerYear)
	{
		super.addItem(name);
		values.add(daysPerYear);
	}
	public double getAge(double days)
	{
		return days/values.get(this.getSelectedIndex());
	}
}

Now lets change it up

See if you can adapt what is going on Planet Choice to have weights, rather than the time (in days) of a year, and also alter AgeApplet so it shows your weight on a selected planet.