Button in Java

import java.awt.*;
import java.awt.event.*;
class Mybuttons extends Frame implements ActionListener
{
Button b1,b2,b3;
Mybuttons()
{
setLayout(new FlowLayout());
b1=new Button("Yellow");
b2=new Button("blue");
b3=new Button("pink");
add(b1);
add(b2);
add(b3);
b1.addActionListener(this);
b2.addActionListener(this);
b3.addActionListener(this);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent We)
{
System.exit(0);
}
});
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource()==b1)setBackground(Color.yellow);
if(ae.getSource()==b2)setBackground(Color.blue);
if(ae.getSource()==b3)setBackground(Color.pink);
}
public static void main(String args[])
{
Mybuttons mb=new Mybuttons();
mb.setSize(400,400);
mb.setTitle("My buttons");
mb.setVisible(true);
}}