UnitConverter.java

import java.awt.*;
import java.applet.*;
import java.awt.event.*;


/**
 * Class UnitConverter - Converts from one unit to another
 * 
 * @author Chris Thiel
 * @version 1.0
 */
public class UnitConverter extends Applet
{
    /**
     * Class That holds the UnitChoice and handles user input
     */

    // instance variables
    private TextField input;
    private Label arrow;
    private Label answer;
    private UnitChoice unitIn;
    private UnitChoice unitOut;
    private Button convertButton;
    private double in;
    private double out;


    public void init()
    {
        input =  new TextField(20);
        input.setText("1");
        add(input);
        unitIn = new UnitChoice();
        unitIn.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ev) 
            {
                repaint();
            }
            });
        add(unitIn);
        arrow=new Label("--->");
        add(arrow);
        answer= new Label("                    ");
        add(answer);
        unitOut = new UnitChoice();
        unitOut.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent ev) 
            {
                repaint();
            }
            });
        add(unitOut);
        convertButton = new Button("Convert");
        convertButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ev) 
        {
            repaint();
        }
        });
        add(convertButton);

    }


    public void paint(Graphics g)
    {
        // simple text displayed on applet
        g.setColor(new Color(255,230,190));
        g.fillRect(0, 0, this.getWidth(), this.getHeight());
        g.setColor(Color.black);
        g.drawString("Unit Converter by Group X", 20, 60);

        try{
        	int x= Integer.parseInt(input.getText() );
        	in=unitIn.toYards(x, unitIn.getSelectedIndex());
            out=unitIn.fromYards(in, unitOut.getSelectedIndex());
            answer.setText(out+" ");
        }catch (Exception e){
        	input.setText("Type a number here");
        	answer.setText(e.getMessage());
        }

    }




}

UnitChoice.java

import java.awt.*;

class UnitChoice extends Choice
    {
        /**
         * Add more choices for more units
         */

        private  double[] yardValues;
        private int count;
        public UnitChoice()
        {
            super();
            yardValues= new double[8];
            count=0;
            addItem("yards", 1.0);
            addItem("inches",36.0);
            addItem("feet", 3.0);
            addItem("rods", 1/5.5);
            addItem("furlongs", 1/220.0);
            addItem("miles", 1/1760.0);

        }
        public void addItem(String name, double yardsValue)
        {

            super.addItem(name);
            yardValues[count]=yardsValue;
            count++;
        }
        public double fromYards( double x, int unit)
        {
          return x*yardValues[unit];   
        }
         public double toYards( double x, int unit)
        {
          return x/yardValues[unit];   
        }
    }