17.3

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class Test_17_3 extends JFrame{    
    private final int YSTART = 20;
    private final int VGAP = 2;
    private final int XGAP = 2;
    private Color myColor = Color.BLACK;
    
    ButtonGroup group = new ButtonGroup();
    JRadioButton jrb1 = new JRadioButton("red");
    JRadioButton jrb2 = new JRadioButton("blue");
    JRadioButton jrb3 = new JRadioButton("yellow");    
    
    trafficPanel tP = new trafficPanel();
    public Test_17_3(){    
        
        JPanel jgButtons = new JPanel();
        jgButtons.setLayout(new GridLayout(1,3));
        jgButtons.add(jrb1);
        jgButtons.add(jrb2);
        jgButtons.add(jrb3);
        
        group.add(jrb1);
        group.add(jrb2);
        group.add(jrb3);    
        
        setLayout(new BorderLayout());
        add(jgButtons,BorderLayout.SOUTH);
        add(tP,BorderLayout.CENTER);    
        
        jrb1.addActionListener(new ActionListener(){

            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                myColor = Color.RED;
                tP.setColor = true;                
                repaint();
            }
            
        });
        jrb2.addActionListener(new ActionListener(){

            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                myColor = Color.BLUE;
                tP.setColor = true;                
                repaint();
            }
            
        });
        jrb3.addActionListener(new ActionListener(){

            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                myColor = Color.YELLOW;
                tP.setColor = true;                
                repaint();
            }
            
        });
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Test_17_3 frame = new Test_17_3();
        frame.setTitle("Test_17_3");
        frame.setSize(300,200);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
    
    
    class trafficPanel extends JPanel{
        public boolean setColor = false;
        
        protected void paintComponent(Graphics g){
            int xCenter = getWidth()/2;
            int yCenter = getHeight()/2;
            
            int radius = getHeight() /6 - 5;
            /** draw steady shape */
            //draw rect
            g.drawRect(xCenter -radius,YSTART, 2*radius,getHeight()-20 -VGAP);
            //draw three circles
            g.drawOval(xCenter - radius + XGAP, YSTART + VGAP, 2*radius -2*XGAP , 2*radius-2*XGAP);
            g.drawOval(xCenter - radius + XGAP, YSTART + 2*radius + 2*VGAP,2*radius -2*XGAP , 2*radius-2*XGAP);
            g.drawOval(xCenter - radius + XGAP, YSTART + 4*radius + 3*VGAP,2*radius -2*XGAP , 2*radius-2*XGAP );
            
            if(setColor)
            {                
                if(myColor == Color.RED)        
                {g.setColor(Color.RED); g.fillOval(xCenter - radius + XGAP, YSTART + VGAP, 2*radius -2*XGAP , 2*radius-2*XGAP);}
                else if(myColor == Color.BLUE)
                {g.setColor(Color.BLUE); g.fillOval(xCenter - radius + XGAP, YSTART + 2*radius + 2*VGAP,2*radius -2*XGAP , 2*radius-2*XGAP);} 
                else
                {g.setColor(Color.YELLOW);g.fillOval(xCenter - radius + XGAP, YSTART + 4*radius + 3*VGAP,2*radius -2*XGAP , 2*radius-2*XGAP );}                                
            }
        }
    }
}