need help with exception

[boki markos]

basically i need to ask the user if they wanna change dimensions of silo 1 and then silo 2.. but i want to put in an exception to catch any numbers, or other characters that arent letters... which exception would i use?

change1 = JOptionPane.showInputDialog("Change Silo 1 dimensions? (y/n)");
        change2 = JOptionPane.showInputDialog(null,"Change Silo 2 dimensions? (y/n)");
        
 
   
     
              
        if (change1.equalsIgnoreCase("y"))
    {
        do
        {
        String input = JOptionPane.showInputDialog("Enter Radius of Silo:1");
        try
            {
               num = Double.parseDouble(input);
            }   
         catch (NumberFormatException nfe)
            {
                JOptionPane.showMessageDialog(null,"That is not an integer, enter radius again");   
            }
         } while(num < 0 );
         Sone.setRadius(num);
         
        do
        {
        String input = JOptionPane.showInputDialog("Enter height of Silo:1");
        try
            {
               num = Double.parseDouble(input);
            }   
         catch (NumberFormatException nfe)
            {
                JOptionPane.showMessageDialog(null,"That is not an integer, enter height again");   
            }
         } while(num < 0);
         Sone.setHeight(num);
    }
         else if(change1.equalsIgnoreCase("n"))
         {
             System.exit(0);
            
            }
            
                     
        
        if (change2.equalsIgnoreCase("y")) 
   {
        do
        {
        String input = JOptionPane.showInputDialog("Enter Radius of Silo:2");
        try
            {
               num = Double.parseDouble(input);
            }   
         catch (NumberFormatException nfe)
            {
                JOptionPane.showMessageDialog(null,"That is not an integer, enter radius again");   
            }
         } while(num < 0);
         Stwo.setRadius(num);
         
        do
        {
        String input = JOptionPane.showInputDialog("Enter Height of Silo:2");
        try
            {
               num = Double.parseDouble(input);
            }   
         catch (NumberFormatException nfe)
            {
                JOptionPane.showMessageDialog(null,"That is not an integer, enter height again");   
            }
         } while(num < 0);
         Stwo.setHeight(num);
   }
   
   else if(change2.equalsIgnoreCase("n"))
         {
             System.exit(0);
            
            }
   
        if (change1.equalsIgnoreCase("y"))
        {
            JOptionPane.showMessageDialog(null,"Silo 1 Dimensions:\n" + "Radius = " + fmt.format(Sone.getRadius()) +
                       "\nHeight = " + fmt.format(Sone.getHeight()) + "\nVolume = " + fmt.format(Sone.getVolume()) +
                       "\nSurface Area = " + fmt.format(Sone.getSurfaceArea()));
        }
        
        if (change2.equalsIgnoreCase("y"))
        {
            JOptionPane.showMessageDialog(null,"Silo 2 Dimensions:\n" + "Radius = " + fmt.format(Stwo.getRadius()) +
                       "\nHeight = " + fmt.format(Stwo.getHeight()) + "\nVolume = " + fmt.format(Stwo.getVolume()) +
                       "\nSurface Area = " + fmt.format(Stwo.getSurfaceArea()));
        }
    }


}

[edit]Add some new lines so as to fit all code into width of screen. CR.[/edit]

[Campbell Ritchie]

I presume you have already initialised num to -1? In which case NumberFormatException looks correct.

But those multiple if-elses don't. Imagine how complicated that would look if you had a silo3 or a silo4. Is there any way of passing a reference to the silo to change, so you can call

s.setHeight(num);

or

s.setRadius(num);

I am not happy to see a System.exit() call. That is probably safe in this instance, but if you have a larger application, you might interfere with other processes going on, and have something disastrous like a file half-written and not properly closed.
There are other dialogs available in JOptionPane; there is one which can return YES/NO, which would probably fit your purposes better than input dialog for getting YES/NO.

[Maneesh Godbole]

You might also want to consider a numeric text field or a JSpinner