The Fahrenheit Applet:


Code:

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

//-------------------------------------------------------------------
//
//  Class Fahrenheit is an applet that accepts temperature in
//  fahrenheit and converts it to celcius.
//
//-------------------------------------------------------------------

public class Fahrenheit extends Applet
   {
   private Label title = new Label ("Fahrenheit to Celcius Converter");
   private Label question = new Label ("Enter Fahrenheit:");
   private Label answer = new Label ("Temperature in Celcius:");

   private TextField fahrenheit = new TextField (5);
   private Label celcius = new Label ("N/A");
   private TextArea log = new TextArea (5, 20);

   private Fahrenheit_Listener listener = new Fahrenheit_Listener (this);

   //===========================================================
   //  Sets up the applet with its various components.
   //===========================================================
   public void init()
   {
      fahrenheit.addActionListener (listener);

      log.setEditable (false);

      add (title);
      add (question);
      add (fahrenheit);
      add (answer);
      add (celcius);
      add (log);

      resize (200,200);

   }

   //===========================================================
   //  Performs the conversion and displays it in the label
   //  and log.
   //===========================================================
   public void convert()
   {
      int fahrenheit_temperature, celcius_temperature;
      String text = fahrenheit.getText();

      fahrenheit_temperature = Integer.parseInt (text);
      celcius_temperature = (fahrenheit_temperature-32)*5/9;

      celcius.setText (Integer.toString (celcius_temperature));
      log.append (text + " converts to " + celcius.getText() + "\n");
   }
}  // class Fahrenheit 


class Fahrenheit_Listener implements ActionListener
{
   private Fahrenheit applet;

   //===========================================================
   //  Sets up the listenter object.
   //===========================================================
   public Fahrenheit_Listener (Fahrenheit listening_applet)
   {
      applet = listening_applet;
   }

   //===========================================================
   //  Calls the conversion method when an action event (the
   //  user pressing enter) occurs.
   //===========================================================
   public void actionPerformed(ActionEvent action)
   {
      applet.convert();
   }
}