单选按钮设置

import java.awt.Dimension;
import java.awt.event.KeyEvent;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;

public class RadioButtonDemo {

    JRadioButton manRadioBuuon, womanRadioButton;
    JLabel label;
    JFrame frame;
    JPanel contentPane;
    private final JRadioButton manRadioButton;

    public RadioButtonDemo() {
        frame = new JFrame("RadioButtonDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        contentPane = new JPanel();
        frame.setContentPane(contentPane);
        label = new JLabel();
        label.setText("性别:");
        manRadioButton = new JRadioButton("男");
        manRadioButton.setMnemonic(KeyEvent.VK_M);
        manRadioButton.setSelected(true);
        womanRadioButton = new JRadioButton("女");
        womanRadioButton.setMnemonic(KeyEvent.VK_W);

        ButtonGroup group = new ButtonGroup();
        group.add(manRadioButton);
        group.add(womanRadioButton);
    }

    public void createAndShowGUI() {

        contentPane.add(label);
        contentPane.add(manRadioButton);
        contentPane.add(womanRadioButton);
        frame.setLocationRelativeTo(label);
        frame.setPreferredSize(new Dimension(300, 200));

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new RadioButtonDemo().createAndShowGUI();
            }

        });
    }
}