TempConverter

TempConverter.java

import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.text.DecimalFormat;

/**
This class displays a window with a slider component.
The user can convert the Celsius temperatures from
0 through 100 to Fahrenheit by moving the slider.
*/

public class TempConverter extends JFrame
{
   private JLabel label1, label2; // Message labels
   private JTextField fahrenheitTemp; // Fahrenheit temp
   private JTextField celsiusTemp; // Celsius temp
   private JPanel fpanel; // Fahrenheit panel
   private JPanel cpanel; // Celsius panel
   private JPanel sliderPanel; // Slider panel
   private JSlider slider; // Temperature adjuster

   /**
Constructor
*/

   public TempConverter()
   {
      // Set the title.
      setTitle("Temperatures");

      // Specify an action for the close button.
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      // Create the message labels.
      label1 = new JLabel("Fahrenheit: ");
      label2 = new JLabel("Celsius: ");

      // Create the read-only text fields.
      fahrenheitTemp = new JTextField("32.0", 10);
      fahrenheitTemp.setEditable(false);
      celsiusTemp = new JTextField("0.0", 10);
      celsiusTemp.setEditable(false);

      // Create the slider.
      slider = new JSlider(JSlider.HORIZONTAL, 0, 100, 0);
      slider.setMajorTickSpacing(20); // Major tick every 20
      slider.setMinorTickSpacing(5); // Minor tick every 5
      slider.setPaintTicks(true); // Display tick marks
      slider.setPaintLabels(true); // Display numbers
      slider.addChangeListener(new SliderListener());

      // Create panels and place the components in them.
      fpanel = new JPanel();
      fpanel.add(label1);
      fpanel.add(fahrenheitTemp);
      cpanel = new JPanel();
      cpanel.add(label2);
      cpanel.add(celsiusTemp);
      sliderPanel = new JPanel();
      sliderPanel.add(slider);

      // Create a GridLayout manager.
      setLayout(new GridLayout(3, 1));

      // Add the panels to the content pane.
      add(fpanel);
      add(cpanel);
      add(sliderPanel);

      // Pack and display the frame.
      pack();
      setVisible(true);
   }

   /**
Private inner class to handle the change events
that are generated when the slider is moved.
*/

   private class SliderListener implements ChangeListener
   {
      public void stateChanged(ChangeEvent e)
      {
         double fahrenheit, celsius;
         DecimalFormat fmt = new DecimalFormat("0.0");

         // Get the slider value.
         celsius = slider.getValue();

         // Convert the value to Fahernheit.
         fahrenheit = (9.0 / 5.0) * celsius + 32.0;

         // Store the celsius temp in its display field.
         celsiusTemp.setText(
                     Double.toString(celsius));

         // Store the Fahrenheit temp in its display field.
         fahrenheitTemp.setText(fmt.format(fahrenheit));
      }
   }

   /*
The main method creates an instance of the
class, which displays a window with a slider.
*/

   public static void main(String[] args)
   {
      new TempConverter();
   }
}