// Fibonacci
// adapted from Deitel
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Fibonacci extends JApplet implements ActionListener {
    JLabel numberLabel;
    JTextField numberField;
    long fibonacciValue;

    public void init() {
      // obtain content pane and set its layout to FlowLayout
      Container container = getContentPane();
      container.setLayout( new FlowLayout() );

      // create numberLabel and attach it to content pane
      numberLabel = new JLabel( "Enter an integer and press Enter" );
      container.add( numberLabel );

      // create numberField and attach it to content pane
      numberField = new JTextField( 3 );
      container.add( numberField );

      // register this applet as numberField’s ActionListener
      numberField.addActionListener( this );
      /*
      // create resultLabel and attach it to content pane
      resultLabel = new JLabel( "Fibonacci value is" );
      container.add( resultLabel );

      // create numberField, make it uneditable
      // and attach it to content pane
      resultField = new JTextField( 15 );
      resultField.setEditable( false );
      container.add( resultField );
      */

   } 

   // obtain user input and call method fibonacci
   public void actionPerformed( ActionEvent event )
   {  
       int number;

      // obtain user’s input and convert to int
      number = Integer.parseInt( numberField.getText() );

      showStatus( "Calculating ..." ); 

      // calculate fibonacci value for number user input
      fibonacciValue = fibonacci( number );

      // indicate processing complete and display result
      showStatus( "" + fibonacciValue );   
    
      //  resultField.setText( Long.toString( fibonacciValue ) );
      repaint();
   }
  
    public void paint (Graphics g) {
	super.paint(g);
	int sqr;
	sqr = (int)Math.sqrt(fibonacciValue);
	g.fillRect(100,100,sqr,sqr);
    }

   public long fibonacci( int n ) {
       long f1=0, f2=1, fn=0;

       if (n == 0) return 0;
       if (n == 1) return 1;

       for (int i=2; i<=n; i++) {
	   fn = f1 + f2;
	   f1 = f2;
	   f2 = fn;
       }
       return fn;
   }

}