[SOLVED] Simple Conversion Calculator

[dbashby]

I have put together a small application converting cm to inches, however I need help resolving 1 error.

I cannot seem to work out what I have done wrong and would appreciate it if you could take a look, I know it is a simple error but I cannot work it out.

Thanks in advance for your help

File attached

[dbashby]

Just incase you dont want to download the file, the formula is in a class

Class - Units
GUI - Application

Netbeans 6.5 was used

code that is causing me the problem is

                          package conversion;
                              import java.text.*;
/**
 *
 * @author Admin
 */
                          public class Application extends javax.swing.JFrame {

    /** Creates new form Application */
                         public Application() {
                         initComponents();
                         }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */

                           private void cmdConvertActionPerformed           (java.awt.event.ActionEvent evt) {                                           
        // Code for converting.   CM TO INCHES -  txtInch    txtCm
                           double inch;
                           double cm;   
                           double outputInches;
                           boolean ok;
                           ok = true;
                           String outinch;

        // try catch for numeric data only
                try {
                cm = Double.parseDouble(txtCm.getText());//expect any numerical input
               }
               catch (NumberFormatException n)  {//to catch none numeric input
                Optpane.showMessageDialog(this,"Enter numbers only please",
                "please re-enter",Optpane.ERROR_MESSAGE); // Optpane kicks in on error
                ok = false; //boolean to trigger Optpane on alpha entry
               }



// start of formula to convert cm to inches and inches to cm - uses class file Units.java
                
                cm=Double.parseDouble(txtCm.getText());


                [COLOR="Green"]outputInches = Units.conversion(cm,inch);[/COLOR]
              

                txtInch.setText(outinch=conversions.format(outputInches));
// End of formula

The line causng the problem is highlighted in green.

[bubbless]

What error do you get?
I would guess a NullPointerExption because Units is not created.

[carderne]

I think the problem is your last statement, a part of which is 'conversions.format(...'

What is 'conversions?'

@bubbless
I don't think so, because Units is a reference to that class, not an object. He just has to ensure that the conversion method in Units is static.

[Fubarable]

Your problem is that Java is case sensitive. Conversion is not the same as conversion. I'd change the case of the method in the Units class to be all lower-case.

In other words, change this:

public static double Conversion(double cm, double inch)
{
  //.... some code
}

to this:

public static double conversion(double cm, double inch)
{
  //.... some code
}

Edit: also, what are you doing with the inches parameter in your conversion method, and the inches variable in your Application class. They both seem superfluous.

[dbashby]

I managed to solve the issue then I also put a calculator as a seperate package together converting the other way round inches to cm

Thanks for your replies.

See attached

[Fubarable]

Please do not cross-post questions in multiple forums. This will frustrate anyone who tries to help you only to find out later that the same answer was given hours ago in a cross-posted thread. For this reason, many volunteers here and at the other sites refuse to help repeat offenders.