ButtonGroup.add(AbstractButton b) has the following syntax.
public void add(AbstractButton b)
In the following code shows how to use ButtonGroup.add(AbstractButton b) method.
import javax.swing.ButtonGroup; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JRadioButton; // w w w. j a va2 s. c o m public class Main extends JPanel { public Main() { JRadioButton radMarriedYes = new JRadioButton("Yes?", true); JRadioButton radMarriedNo = new JRadioButton("No?", false); JRadioButton radGolfYes = new JRadioButton("Yes?", false); JRadioButton radGolfNo = new JRadioButton("No?", true); ButtonGroup radioGroup1 = new ButtonGroup(); ButtonGroup radioGroup2 = new ButtonGroup(); setLayout(null); add(radMarriedYes); add(radMarriedNo); add(radGolfYes); add(radGolfNo); radioGroup1.add(radMarriedYes); radioGroup1.add(radMarriedNo); radioGroup2.add(radGolfYes); radioGroup2.add(radGolfNo); radMarriedYes.setBounds(30, 50, 50, 20); radMarriedNo.setBounds(30, 80, 50, 20); radGolfYes.setBounds(150, 50, 50, 20); radGolfNo.setBounds(150, 80, 50, 20); } public static void main(String[] args) { JFrame frame = new JFrame(); frame.getContentPane().add(new Main()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(200, 200); frame.setVisible(true); } }