import java.awt.*;
import java.awt.event.*;
import java.math.*;

import javax.swing.*;

public class Fib {
    
    public static void main(String[] args) {
        JFrame frame = new JFrame("Fibonacci Numbers");
        frame.setVisible(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JComponent c = new JPanel(new BorderLayout());
        frame.setContentPane(c);
        final JTextArea t = new JTextArea();
        c.setPreferredSize(new Dimension(600,400));
        JScrollPane sp = new JScrollPane(t);         
        c.add(sp, BorderLayout.CENTER);
        final JSlider slider = new JSlider(JSlider.VERTICAL,1,200,7);
        slider.setPaintLabels(true);
        slider.setMajorTickSpacing(10);
        slider.setSnapToTicks(true);
        slider.setMinorTickSpacing(1);
        slider.setPaintTicks(true);
        JButton but = new JButton("Start");
        c.add(slider, BorderLayout.EAST);
        c.add(but, BorderLayout.SOUTH);    
        frame.pack();
        frame.setVisible(true);
        but.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                new Thread(new Runnable() {
                    public void run() {
                        int n = slider.getValue();
                        t.setText("fibLinear("+n+") = ");
                        t.append(fibFast(n)+"\n");
                        if (n < 40) {
                            t.append("fibNonLinear("+n+") = ");
                            t.append(fib(n).toString());
                        }
                    }
                }).start();
            }                              
        });        
    }


    private static BigInteger fib(int n) {
      if (n <= 1) {
          return BigInteger.ONE;
      } else {
          return  fib(n-1).add(fib(n-2));
      }
    }
    
    private static BigInteger fibFast(int n) {
        BigInteger fibi = BigInteger.ONE;
        BigInteger fibii = fibi;
        BigInteger tmp;
        for (int i=0; i<n; i++) {
            tmp = fibii;
            fibii = fibi.add(fibii);
            fibi = tmp;
        }
        return fibi;
    }

    
}