Question

I have a JTextField that I’m not always passing a value to, but it causes a NumberFormatException error to be thrown when the program runs if the person hasn’t entered anything into the JTextField. I have some code below that I’m trying to convert a null response into a different String value. Why isn’t it assigning stringInput as a String of “0”?

public int getOptionalDinners()
{
  try
  {     
  // get the input from the text field and determine if it's more than 0
  String stringInput = " ";
  stringInput = dinnerTextField.getText();
  if (stringInput == null)
     stringInput = "0";
  int validAmount = Integer.parseInt(stringInput);
  if (validAmount < 0)
     throw new IllegalArgumentException();
  dinnerQuantity = validAmount * 30;
  }
  catch (NumberFormatException error)
    {
       JOptionPane.showMessageDialog (null, "The number of dinners needs to be numeric.", 
           "Input Error", JOptionPane.ERROR_MESSAGE);
    }
  catch (IllegalArgumentException error)
    {
      JOptionPane.showMessageDialog (null, "The number of dinners needs to be higher than 0.", 
           "Input Error", JOptionPane.ERROR_MESSAGE);
    }

  return dinnerQuantity;
}

Answer 1

try

if (stringInput == null || stringInput.length() == 0)  {
  stringInput = "0";
}

You also need to check if it is 0 length.

Then assign the value back to the JTextField.

dinnerTextField.setText(stringInput);