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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;



public class Singleton extends JFrame
{

    int a = 1;
    private JTextField titleField;
    
    private static Singleton singleton=null;
    
    private JButton jb;

    private Singleton()    {
        JPanel p = new JPanel();
        p.setLayout(new GridLayout(3,1));
        p.add(new JLabel("Book title:"));
        this.titleField = new JTextField(15);
        this.jb = new JButton();
        p.add(this.titleField);
        jb.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                try {
                    a++;
                    String s = new String();
                    Integer i = new Integer(a);
                    titleField.setText(i.toString());
                }
                catch (Exception e) {
                }
            }
        });
        p.add(jb);
        Integer i = new Integer(a);
        titleField.setText(i.toString());
        this.add(p);
    }

    public static Singleton instance()
    {
        if(singleton==null)
            singleton = new Singleton();
        return singleton;
    }

    
    public static void main(String[] args) {
          instance().show();
    }

}