code: public void focusLost(FocusEvent focusEvent) {
  		String text = ((JSpinner.DateEditor) getEditor()).getTextField()
  				.getText();
  		if (text.length() == 0) {
  			setDate(null);
  		}
  	}
docs: /*
  (non-Javadoc)
  
  @see java.awt.event.FocusListener#focusLost(java.awt.event.FocusEvent)