Question 5

bulb.java

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

public class bulb extends JFrame implements ActionListener 
   {
    JButton b1, b2;
    Signal on = new Signal(Color.blue);
    public bulb()
        {
          super("POWER SWITCH");
          getContentPane().setLayout(new GridLayout(3,5));
          b1 = new JButton("ON");
          b2 = new JButton("OFF");
          b1.addActionListener(this);
          b2.addActionListener(this);        
          on.turnOn(false);
        
          JPanel p1 = new JPanel(new GridLayout(1,1));
          p1.add(on);
          JPanel p2 = new JPanel(new FlowLayout());
          p2.add(b1);
          p2.add(b2);

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


    public static void main(String[] args)
      {
        bulb tl = new bulb();        
        tl.setVisible(true);
      }    
    
    public void actionPerformed(ActionEvent e)
       {        
        if (e.getSource() == b1)
           {
             on.turnOn(true);
           } 
       
        else if (e.getSource() == b2)
        {
            on.turnOn(false);            
        } 
    }
}     
    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.black );
        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 );
    }
}