import java.io.*;
import java.text.*;
import java.awt.event.*;
import java.awt.*;

/* The TempConvert class is a frame.  It displays two labels, two text boxes and a button.  When the button is clicked, the number in the first box is converted from Fahrenheit to Celsius. */
class TempConvert extends Frame
{
     private Button convert;
     private Label fahrenheitLabel, celsiusLabel;
     private TextField fahrenheit, celsius;
     private Panel panel;
 
     /* The constructor first adds a listener to the window so that clicking the closing icon will close the window.  It then creates a panel and adds the labels, text boxes and button to the panel.  A listener is added to the button and the panel is added to the frame. */
     TempConvert ()
     {
          super ("Temperature Conversion");
          setSize (200, 200);

          // Add a window closer to the frame.
          addWindowListener (new WindowAdapter() {public void windowClosing(WindowEvent e) {System.exit(0);}});

          // Get a new panel and set its background color.
          panel = new Panel ();
          panel.setBackground (Color.cyan);

          // Get the labels and text boxes and add them to the panel.
          fahrenheitLabel = new Label ("Fahrenheit");
          fahrenheit = new TextField (10);
          panel.add (fahrenheitLabel); panel.add (fahrenheit);
          celsiusLabel = new Label ("Celsius");
          celsius = new TextField (10);
          panel.add (celsiusLabel); panel.add (celsius);

          // Get a new button and add a listener to it.
          convert = new Button ("Convert");
          convert.addActionListener (new ConversionListener ());
          panel.add (convert);

          // Add the panel to the frame.
          add (panel);
     } // constructor

     // Inner class to listen for the convert button.
     class ConversionListener implements ActionListener
     {
          public void actionPerformed (ActionEvent event)
          {
               try
               {
                    double f, c;
                    f = Double.parseDouble (fahrenheit.getText ());
                    c = (f - 32) * 5 / 9;
                    celsius.setText ("" + decimals (c));
               } catch (NumberFormatException e) {celsius.setText ("Error");}
          } // method actionPerformed
     } // class ConversionListener
 
     // Formats a double for string output with two decimal places.
     public static String decimals (double num)
     {
          DecimalFormat decFor = new DecimalFormat ();
          decFor.setMaximumFractionDigits (2);
          decFor.setMinimumFractionDigits (2);
          return decFor.format (num);
     } // decimals

     // The main method gets a new frame and shows it.
     public static void main (String [] args)
     {
          TempConvert frame = new TempConvert ();
          frame.show ();
     }
} // class TempConversion