用java编写交通信号灯

按照你的要求编写的红绿灯程序，你看看吧，比较简单。
完整的程序如下：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.Graphics;
public class TrafficLight extends JFrame{
JRadioButton jrbYellow,jrbGreen,jrbRed;
int flag=0;
jpNewPanel jpNewPanel;
public static void main(String[] args){
TrafficLight frame=new TrafficLight();
frame.setSize(500,200);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle(TrafficLight);
frame.setVisible(true);
}
public TrafficLight(){
jpNewPanel=new jpNewPanel();
add(jpNewPanel,BorderLayout.CENTER);
JPanel jpRadioButtons=new JPanel();
jpRadioButtons.setLayout(new GridLayout(1,3));
jpRadioButtons.add(jrbYellow=new JRadioButton(Yellow));
jpRadioButtons.add(jrbGreen=new JRadioButton(Green));
jpRadioButtons.add(jrbRed=new JRadioButton(Red));
add(jpRadioButtons,BorderLayout.SOUTH);
ButtonGroup group=new ButtonGroup();
group.add(jrbYellow);
group.add(jrbGreen);
group.add(jrbRed);

jrbYellow.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
flag=2;
jpNewPanel.repaint();
}
});
jrbGreen.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
flag=1;
jpNewPanel.repaint();
}
});
jrbRed.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
flag=3;
jpNewPanel.repaint();
}
});
}
class jpNewPanel extends JPanel{
protected void paintComponent(Graphics g){
super.paintComponent(g);
g.drawRect(0,0,40,100);
g.drawOval(10,10,20,20);
g.drawOval(10,40,20,20);
g.drawOval(10,70,20,20);
if(flag==1){
g.setColor(Color.GREEN);
g.fillOval(10, 70, 20, 20);
}
else if(flag==2){
g.setColor(Color.YELLOW);
g.fillOval(10, 40, 20, 20);
}
else if(flag==3){
g.setColor(Color.RED);
g.fillOval(10, 10, 20, 20);
}
}
}
}