I am supposed to meet these requirements for my trafficlight project... I need h

Question

I am supposed to meet these requirements for my trafficlight project... I need help fixing my code to meet them:

-Write an event driven program

-Use if statement or switch statement

-Use JPanel

-Use Flowlayout for placing JButtons on JPanel

-Use Borderlayout

This is my program:

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

public class TrafficLight extends JFrame implements ActionListener {
JButton b1, b2, b3;

Signal green = new Signal(Color.green);
Signal yellow = new Signal(Color.yellow);
Signal red = new Signal(Color.red);

public TrafficLight(){
super("Traffic Light");
getContentPane().setLayout(new GridLayout(2, 1));
b1 = new JButton("STOP!");
b2 = new JButton("WAIT!");
b3 = new JButton("GO!");
b1.addActionListener(this);
b2.addActionListener(this);
b3.addActionListener(this);

green.turnOn(false);
yellow.turnOn(false);
red.turnOn(true);

JPanel p1 = new JPanel(new GridLayout(3,1));
p1.add(red);
p1.add(yellow);
p1.add(green);
JPanel p2 = new JPanel(new FlowLayout());
p2.add(b1);
p2.add(b2);
p2.add(b3);

getContentPane().add(p1);
getContentPane().add(p2);
pack();
}

public static void main(String[] args){
TrafficLight tl = new TrafficLight();
tl.setVisible(true);
}
public void actionPerformed(ActionEvent e){
if (e.getSource() == b1){
green.turnOn(false);
yellow.turnOn(false);
red.turnOn(true);
} else if (e.getSource() == b2){
yellow.turnOn(true);
green.turnOn(false);
red.turnOn(false);
} else if (e.getSource() == b3){
red.turnOn(false);
yellow.turnOn(false);
green.turnOn(true);
}
}
}   
class Signal extends JPanel{

Color on;
int radius = 30;
int border = 10;
boolean change;

Signal(Color color){
on = color;
change = true;
}

public void turnOn(boolean a){
change = a;
repaint();
}

public Dimension getPreferredSize(){
int size = (radius+border)*2;
return new Dimension( size, size );
}

public void paintComponent(Graphics g){
g.setColor( Color.pink );
g.fillRect(0,0,getWidth(),getHeight());

if (change){
g.setColor( on );
} else {
g.setColor( on.darker().darker().darker() );
}
g.fillOval( border,border,2*radius,2*radius );
}

Can you help fix what I am missing??

Explanation / Answer

/* Your program is meeting all the requirements except usage of Border layout. By default JFrame uses Border Layout , so we don't need to set any layout to content pane explicitly. Please find the changes, in the constructor for adding JPanels to the content pane. */

import java.awt.*;

import javax.swing.*;

import java.awt.event.*;

import javax.swing.border.*;

public class TrafficLight extends JFrame implements ActionListener {

JButton b1, b2, b3;

Signal green = new Signal(Color.green);

Signal yellow = new Signal(Color.yellow);

Signal red = new Signal(Color.red);

public TrafficLight(){

super("Traffic Light");

/* We don't need to set any layout since by default Border Layout is set */

b1 = new JButton("STOP!");

b2 = new JButton("WAIT!");

b3 = new JButton("GO!");

b1.addActionListener(this);

b2.addActionListener(this);

b3.addActionListener(this);

green.turnOn(false);

yellow.turnOn(false);

red.turnOn(true);

JPanel p1 = new JPanel(new GridLayout(3,1));

p1.add(red);

p1.add(yellow);

p1.add(green);

JPanel p2 = new JPanel(new FlowLayout());

p2.add(b1);

p2.add(b2);

p2.add(b3);

getContentPane().add(p1, BorderLayout.CENTER); /*Adding Signals at the center of Border layout */

getContentPane().add(p2, BorderLayout.SOUTH); /*Adding Signals at the bottom of Border layout */

pack();

}

public static void main(String[] args){

TrafficLight tl = new TrafficLight();

tl.setVisible(true);

}

public void actionPerformed(ActionEvent e){

if (e.getSource() == b1){

green.turnOn(false);

yellow.turnOn(false);

red.turnOn(true);

} else if (e.getSource() == b2){

yellow.turnOn(true);

green.turnOn(false);

red.turnOn(false);

} else if (e.getSource() == b3){

red.turnOn(false);

yellow.turnOn(false);

green.turnOn(true);

}

}

}   

class Signal extends JPanel{

Color on;

int radius = 30;

int border = 10;

boolean change;

Signal(Color color){

on = color;

change = true;

}

public void turnOn(boolean a){

change = a;

repaint();

}

public Dimension getPreferredSize(){

int size = (radius+border)*2;

return new Dimension( size, size );

}

public void paintComponent(Graphics g){

g.setColor( Color.pink );

g.fillRect(0,0,getWidth(),getHeight());

if (change){

g.setColor( on );

} else {

g.setColor( on.darker().darker().darker() );

}

g.fillOval( border,border,2*radius,2*radius );

}

}

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