JRadioButton radio1 = new JRadioButton("radio bottone 1");
        JRadioButton radio2 = new JRadioButton("radio botton 2");
        JRadioButton radio3 = new JRadioButton("radio bottone 3");

ButtonGroup btg = new ButtonGroup();
        btg.add(radio1);
        btg.add(radio2);
        btg.add(radio3);