import  javax.swing.*;
 import  java.awt.event.ActionListener;
 import  java.awt.event.ActionEvent;
 import  java.awt.*;


 public   class  Main2 {
    JFrame jf; // main frame
    JPanel jp; // buttons panel

    // class constuctor
     public  Main2(){
        jf =  new  JFrame("button add demo");
        jp =  new  JPanel();
        jp.setLayout( new  BoxLayout(jp, BoxLayout.PAGE_AXIS));

        JButton jb = addButton("First button", jp);
        jb.addActionListener( new  ButtonActionListener());
        jp.add(jb);
        jf.getContentPane().add(jp);
        
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.pack();
        jf.setSize( new  Dimension( 400 , 300 ));
        jf.setVisible(true);
    }
    
    // add a button to given container
    JButton addButton(String text, Container cont) {
        JButton jb =  new  JButton(text);
        jb.setAlignmentX(Component.CENTER_ALIGNMENT);
        cont.add(jb);
         return  jb;
    }
    
    
     public   static   void  main(String[] args) {
        SwingUtilities.invokeLater( new  Runnable(){
             public   void  run() {
                 new  Main2();
            }
        });
    }

   // ActionListner for first button
     private   class  ButtonActionListener  implements  ActionListener {
         public   void  actionPerformed(ActionEvent e) {
            addButton("Next button",jp);
            jp.revalidate();
        }
    }
}