Errors in my temperature converter

Question

Today I am playing with a class that converts Fahrenheit to Celsius. I understand that the formula for Fahrenheit to Celsius is: (5/9)*(deg F-32)
Here is my class:
import javax.swing.JOptionPane;
public class TConverter {
     public static void main(String[] args) {
          double Fahrenheit=98.6;
          double Celsius=(5/9)*(Fahrenheit-32);
          JOptionPane.showMessageDialog(null,Celsius);
I have two problems:
1) the result I get is always 0. Why?
2) I get an error on the line:
JOptionPane.showMessageDialog(null, Celsius);unless I enter some type of string:
JOptionPane.showMessageDialog(null, "Celsius: " + Celsius);Does that mean that in JOptionPane.showMessageDialog I must always have a string to be able to use it?
Message was edited by:
Lavazza

Answer 1

1) the result I get is always 0. Why?
The error is that the division 5/9 is evaluated as a division between integer... so you have to explictilly specify a cast to double in order to not obtain 0
2) I get an error on the line:
JOptionPane.showMessageDialog(null,
Celsius);unless I enter some type of string:
JOptionPane.showMessageDialog(null, "Celsius:
" + Celsius);Does that mean that in JOptionPane.showMessageDialog
I must always have a string to be able to use it?
The problem is that the method showMessageDialog accept (you can see documentation) an Object like second parameter... and double is not an Object but it's a primitive type. Convert it to an object using the utility class Double.
Belowe I put the right implementation.
Bye
Diego
import javax.swing.JOptionPane;
public class TConverter {
     public static void main(String[] args) {
          double Fahrenheit=98.6;
          double Celsius= ((double)5/9)*(Fahrenheit-32);
          JOptionPane.showMessageDialog(null,new Double(Celsius));
}