JOption Pane problem

[Dan Grindstaff]

Hello All, I am trying to get the following code to compile and run, I am getting an error message:

Exception in thread "main" java.lang.IllegalArgumentException: 
Cannot format given Object as a Number
	at java.text.DecimalFormat.format(Unknown Source)
	at java.text.Format.format(Unknown Source)
	at Converter.main(Converter.java:55)

Here is the code:

import java.awt.Component;
import javax.swing.JOptionPane;
import java.text.DecimalFormat;

public class Converter {

private static Component frame;

/** Creates a new instance of Converter */
public Converter() {
}

// Method to convert from degrees Celcius to degrees Fahrenheit
public static float celciusToFahrenheit(String output)
{
	float f = 0.0f;
	try {
	f = Float.parseFloat(output);
	}
	catch (NumberFormatException e) {
	// Output doesn't contain a valid float so do some error recovery here
	}
float degFahrenheit;
degFahrenheit = f * 9/5 + 32;
return degFahrenheit;
}

// Method to convert from degrees Fahrenheit to degrees Celcius
public static float fahrenheitToCelcius(float degFahrenheit)
{
float degCelcius;
degCelcius = (degFahrenheit - 32) * 5/9;
return degCelcius;
}

// Main method demonstrating usage of above methods
public static void main(String[] args)
{
//Custom button text
Object[] options = {"*C to *F",
"*F to *C"};
int button = JOptionPane.showOptionDialog(frame, 
"How would you like to convert?",
"Temerature Conversion",
JOptionPane.YES_NO_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE,
null,
options,
options[1]);
if (button == 0)
{
String degree = JOptionPane.showInputDialog("Enter in the Celcius value:");
String degreeValue = "Celcius";
DecimalFormat df = new DecimalFormat("0.00");
String output = df.format(degree);
JOptionPane.showMessageDialog(frame, "The Fahrenheit value is " + celciusToFahrenheit(output));
}
else
{
String degree = JOptionPane.showInputDialog("Enter in the Fahrenheit value:");
String degreeValue = "Fahrenheit";
DecimalFormat df = new DecimalFormat("0.00");
String output = df.format(degree);
JOptionPane.showMessageDialog(frame, "The Celsius value is " + fahrenheitToCelcius(output));
}
}
}

[Dan Grindstaff]

OK, I figured out what was causing the problem, but now I would like to make a third JOptionpane that asks "would you like to try again?". The program should not end until the user selects 'no'.

Here is the cleaned up code:

    
import java.awt.Component;
import javax.swing.JOptionPane;


public class Converter {

private static Component frame;

/** Creates a new instance of Converter */
public Converter() {
}

// Method to convert from degrees Celcius to degrees Fahrenheit
public static float celciusToFahrenheit(String output)
{
	float f = 0.0f;
	try {
	f = Float.parseFloat(output);
	}
	catch (NumberFormatException e) {
	// Output doesn't contain a valid float so do some error recovery here
	}
float degFahrenheit;
degFahrenheit = f * 9/5 + 32;
return degFahrenheit;
}

// Method to convert from degrees Fahrenheit to degrees Celcius
public static float fahrenheitToCelcius(String output)
{
	float f = 0.0f;
	try {
	f = Float.parseFloat(output);
	}
	catch (NumberFormatException e) {
	}
float degCelcius;
degCelcius = (f - 32) * 5/9;
return degCelcius;
}

// Main method demonstrating usage of above methods
public static void main(String[] args)
{
//Custom button text
Object[] options = {"*C to *F", "*F to *C"};
int button = JOptionPane.showOptionDialog(frame,"How would you like to convert?","Temerature Conversion",
JOptionPane.YES_NO_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE,
null,
options,
options[1]);
if (button == 0)
{
String degree = JOptionPane.showInputDialog("Enter in the Celcius value:");
JOptionPane.showMessageDialog(frame, "The Fahrenheit value is " + celciusToFahrenheit(degree));
}
else
{
String degree = JOptionPane.showInputDialog("Enter in the Fahrenheit value:");
JOptionPane.showMessageDialog(frame, "The Celsius value is " + fahrenheitToCelcius(degree));
}
}
}

[Steve Luke]

    String degree = JOptionPane.showInputDialog("Enter in the Fahrenheit value:");
    String degreeValue = "Fahrenheit";
    DecimalFormat df = new DecimalFormat("0.00");
    String output = df.format(degree);

What does df.format(...) do? You should read the method's API: Format#format(...)

[Maneesh Godbole]

Dan,
In future, while posting code please do use code tags

[Campbell Ritchie]

And I think this thread would sit better on the Swing forum. Moving.

[Dan Grindstaff]

Thanks, all for your help. I am still wondering how to get a JOptionpane to persist. I want there to be a 'master' JOptionpane that asks something like 'would you like to try again?' and if no exit program. TIA.

[Michael Dunn]

wrap what you want to persist in a do/while

simple demo

    
class Testing
{
  public static void main(String[] args)
  {
    int x = 0;
    do
    {
      System.out.println(x++);
    }while(javax.swing.JOptionPane.showConfirmDialog(null,"Another?","",
      javax.swing.JOptionPane.YES_NO_OPTION) == javax.swing.JOptionPane.YES_OPTION);
    System.exit(0);
  }
}

[Dan Grindstaff]

Thanks! Works like a charm.