filler code

        cancelButton = new JButton("Cancel");
        GridBagConstraints cancelButtonConstraints = new GridBagConstraints();
        cancelButtonConstraints.gridx = 0;
        cancelButtonConstraints.gridy = 0;
        leftButtonGroup.add(cancelButton, cancelButtonConstraints);

        JLabel leftButtonGroupFiller = new JLabel(" ");
        GridBagConstraints leftFillerConstraints = new GridBagConstraints();
        leftFillerConstraints.fill = GridBagConstraints.BOTH;
        leftFillerConstraints.weightx = 1;
        leftFillerConstraints.gridx = 1;
        leftFillerConstraints.gridy = 0;
        leftButtonGroupFiller.setBorder(new BevelBorder(BevelBorder.LOWERED));
        leftButtonGroup.add(leftButtonGroupFiller, leftFillerConstraints);