//RadioButtonExample.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class RadioButtonExample
{  
	public static void main(String[] args)
	{  
		RadioButtonFrame frame = new RadioButtonFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.show();
	}
}

class RadioButtonFrame extends JFrame
{
	public RadioButtonFrame()
	{
		setTitle("RadioButtonExample");
		setSize(WIDTH, HEIGHT);

		Container contentPane = getContentPane();

		//新建標簽
		myLabel = new JLabel("Origin choice: EAST", JLabel.CENTER);
		contentPane.add(myLabel, BorderLayout.CENTER);

		//建立容器面板
		radioPanel = new JPanel();

		//新建單選按鈕
		myButtonGroup = new ButtonGroup();
		addRadioButton("EAST" , true, "EAST");
		addRadioButton("SOUTH" , false, "SOUTH");
		addRadioButton("WEST" , false, "WEST");
		addRadioButton("NORTH" , false, "NORTH");

		contentPane.add(radioPanel, BorderLayout.SOUTH);
	}

	//將單選按鈕加入到按鈕組中
	public void addRadioButton(String name, boolean defaultRadio, String show)
	{
		final String showLabel = show;

		JRadioButton button = new JRadioButton(name, defaultRadio);
		myButtonGroup.add(button);
		radioPanel.add(button);
		
		//添加事件監聽器
		button.addActionListener(new ActionListener()
		{
			public void actionPerformed(ActionEvent evt)
			{
				myLabel.setText("You choosed: " + showLabel);
			}
		});
	}

	public static final int WIDTH = 300;
	public static final int HEIGHT = 140;

	private JLabel myLabel;
	private ButtonGroup myButtonGroup;
	private JPanel radioPanel;
}