title: Fahrenheit to Celsius conversion yields only 0.0 and -0.0
body: <p>I'm on the 8th chapter (Methods, Constructors, and Fields) of my Java methods book and I'm having a problem with one of my exercises. </p>
  
  <p>The provided code is Temperature.java</p>
  
  <pre><code>  import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
    import java.text.DecimalFormat;
  
    public class Temperature extends JApplet
     implements ActionListener {
        private JTextField displayF, displayC;
        private static DecimalFormat displayFormat = new DecimalFormat("0.0");
  
        public void init() {
            Container c = getContentPane();
            c.setBackground(Color.white);
            c.setLayout(new GridLayout(2, 2, 10, 0));
  
            c.add(new JLabel("  Fahrenheit:"));
            c.add(new JLabel("  Celsius:"));
  
            displayF = new JTextField(6);
            displayF.setBackground(Color.yellow);
            displayF.addActionListener(this);
            c.add(displayF);
  
            displayC = new JTextField(6);
            displayC.setBackground(Color.yellow);
            displayC.addActionListener(this);
            c.add(displayC);
        }
  
        public void actionPerformed(ActionEvent e) {
            String s;
            double degrees;
            FCConverter fc = new FCConverter();
  
            if ((JTextField) e.getSource() == displayF) {
                s = displayF.getText().trim();
                degrees = Double.parseDouble(s);
                fc.setFahrenheit(degrees);
                degrees = fc.getCelsius();
                displayC.setText(displayFormat.format(degrees));
            } else {
                s = displayC.getText().trim();
                degrees = Double.parseDouble(s);
                fc.setCelsius(degrees);
                degrees = fc.getFahrenheit();
                displayF.setText(displayFormat.format(degrees));
            }
        }
    }
  </code></pre>
  
  <p>And from there I'm supposed to write and test FCConverter.java
  I've come up with:</p>
  
  <pre><code>import java.awt.*;
  import java.awt.event.*;
  import javax.swing.*;
  import java.text.DecimalFormat;
  
  public class FCConverter
  {
    private double Celsius;
    private double Fahrenheit;
    public double setFahrenheit (double degrees)
    {
        Celsius = (degrees - 32) * (5 / 9);
        return 0;
    }
    public double getCelsius ()
    {
        return Celsius;
    }
    public double setCelsius (double degrees)
    {
    Fahrenheit = (degrees * 9 / 5 + 32);
            return 0;
    }
    public double getFahrenheit ()
    {
        return Fahrenheit;
    }
  }
  </code></pre>
  
  <p>It's probably horrendous in terms of style, but I just wanted to get some working code that got past the compiler (hence the "return 0;"s which I'm fairly certain can be circumvented in a much more fashionable manner).</p>
  
  <p>What I want to know is, when I test this in appletviewer or in browser form, the Celsius to Fahrenheit conversion works fine, but the Fahrenheit to Celsius conversion yields only 0.0 and -0.0. I don't understand what's wrong since the part I've designed seems fairly symmetrical. Shouldn't it be the case that both or neither conversion method works? </p>