java.lang.NoSuchMethodError: main Exteption in thread main

Når jeg kører nedenstående eksempel får jeg fejlen: java.lang.NoSuchMethodError: main o.s.v. Jeg bruger Forte og har lavet masser af andre appletter der virker fint. Eksemplet er hentet direkte fra "Java how to program" Jeg bruger J2SDK 1.3.1  Hvad er der galt ?

import java.awt.Container;
// Java extension packages
import javax.swing.*;
public class Maximum2 extends JApplet {
  // initialize applet by obtaining user input and creating GUI
  public void init()
  {
      // obtain user input
      String s1 = JOptionPane.showInputDialog(
        "Enter first floating-point value" );
      String s2 = JOptionPane.showInputDialog(
        "Enter second floating-point value" );
      String s3 = JOptionPane.showInputDialog(
        "Enter third floating-point value" );

      // convert user input to double values
      double number1 = Double.parseDouble( s1 );
      double number2 = Double.parseDouble( s2 );
      double number3 = Double.parseDouble( s3 );
      // call method maximum to determine largest value
      double max = maximum( number1, number2, number3 );
      // create JTextArea to display results
      JTextArea outputArea = new JTextArea();
      // display numbers and maximum value
      outputArea.setText( "number1: " + number1 +
        "\nnumber2: " + number2 + "\nnumber3: " + number3 +
        "\nmaximum is: " + max );

      // get the applet's GUI component display area
      Container container = getContentPane();

      // attach outputArea to Container c
      container.add( outputArea );

  }  // end method init

  // maximum method uses Math class method max to help
  // determine maximum value
  public double maximum( double x, double y, double z )
  {
      return Math.max( x, Math.max( y, z ) );
  }  // end method maximum
}  // end class Maximum