How to check manual edits on a JSpinner field using DefaultEditor approach

Question 1

Custom DocumentListeners and formattedTextField don't play nicely with each other, better don't mix. Instead, use a PropertyChangeListener on the text field that listens for changes of its editValid property: whenever that changes to false, you could notify the users

field.addPropertyChangeListener(new PropertyChangeListener() {

    @Override
    public void propertyChange(PropertyChangeEvent evt) {
        LOG.info("" + evt);
        if ("editValid".equals(evt.getPropertyName()) 
            &&  Boolean.FALSE.equals(evt.getNewValue())) {
          SpinnerNumberModel model = (SpinnerNumberModel) spin2.getModel();  
          JOptionPane.showMessageDialog(null,
          "Error: Number must be in range [" + model.getMinimum() + " ..." + model.getMaximum() + "]",
           "Error Massage",
          JOptionPane.ERROR_MESSAGE);

        }

    }
});

BTW, personally, I agree with Mad - such an intrusive notification tends to annoy me and maybe your users as well ..

Question 2

You have a few basic choices.

You could trap the exception
You could check for a "empty" String

Personally, I'd like to do both...

public void warn() {
    String text = ((JSpinner.DefaultEditor)spin2.getEditor()).getTextField().getText();
    if (text != null && !text.trim().isEmpty()) {
        try {
            int stringValue = Integer.parseInt(text);
            JOptionPane.showMessageDialog(null,
                  "VALS: "+spin2.getValue(), "Error Massage",
                  JOptionPane.ERROR_MESSAGE);
            if (stringValue<10 || stringValue >100){
            JOptionPane.showMessageDialog(null,
              "Error: Please enter number bigger than 0", "Error Massage",
              JOptionPane.ERROR_MESSAGE);
            }
        } catch (NumberFormatException exp) {
            exp.printStackTrace();
        }
    }
}

Now, as a user, this is likely just to annoy me. Highlight the field, beep, change the tooltip, sure, throw a dialog in my face...hmmm...

You could take a look at Validating Input, which will allow you to validate the input when the field loses focus, which, personally, might be a better choice.

If you don't particularly need to functionality of the JSpinner (running values up and down in a sequence), you could take a look at using a DocumentFilter (for examples), which will allow you to control what goes into the field. You should know that it's not possible (or close enough to it) to add a DocumentFilter to a JSpinner... :P

Question 3

The Exception says that the String you pass to Integer.parseInt(..) is an empty string. So make sure to check ((JSpinner.DefaultEditor)spin2.getEditor()).getTextField().getText() for null and empty before passing it to Integer.parseInt(..)

You may have a look at apache commons-io and the StringUtils class, they have quite a few good methods to ease the pain on checking for empty/blank strings

Question 4

This proved to be a huge pain the rear. I wanted to color my text field background immediately. Ended up making an editor that overrode the editor I wanted to use, then setting it as the spinners editor accordingly. Seems to be working for me so far.

Add a java class with the following (remove the quotes around the code block, I'm having a hard time with stack overflow's editor):

`public class CustomNumberEditor extends JSpinner.NumberEditor {
    public CustomNumberEditor( JSpinner spinner ) {
        super( spinner );
        ((DefaultFormatter ) ((JFormattedTextField) getComponent( 0 )).getFormatter()).setCommitsOnValidEdit( true );
    }
    @Override public void propertyChange(PropertyChangeEvent e) {
        super.propertyChange( e );
        if( e.getPropertyName().equals( "value" ) )
            doStuff( (int) e.getNewValue() );
    }
    private void doStuff( int value )
    {
        //do stuff
    }
}`

Then when adding your spinner, do this:

_quantitySpinner.setEditor(new CustomNumberEditor(_quantitySpinner));