// Java 2

// Toy example of a program usable as an application or as an applet.
// Flexible is the program proper, such as it is.
// GUI is the graphical user interface, such as it is.

import java.lang.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;

//-----------------------------------------------------------------------------

public class Flexible extends Applet
 { static int s = 0;  // stands for the State of the computation
   static GUI gui;    // the GUI controls the computation

   // main & init would also initiate some "real" computation in a real problem

   public static void main(String[] argv)        // required for an application
    { gui = new GUI(null);
    }//main

   public void init()                                 // required for an applet
    { gui = new GUI(this);
    }//init


   // The routines below would do some "real" computing in a real problem:

   public static void action1() { s++; }  // example computation

   public static void action2() { s--; }  // -- " --

 }//Flexible class

//-----------------------------------------------------------------------------
// java.lang.Object
//  |-java.awt.Component
//     |-java.awt.Container  --lowest common ancestor of Applet & Frame
//        |
//        |-java.awt.Panel
//        |  |-java.applet.Applet
//        |
//        |-java.awt.Window
//           |-java.awt.Frame

class GUI
 { public Container c; // either the applet or a new frame
   boolean isFrame = false;
   Label stateDisplay;

   public GUI(Container c)
    { if(c == null) // called from main(), i.e. an application, not applet
       { final Frame f = new Frame(); f.setTitle("Flexible");
         f.addWindowListener(
            new WindowAdapter()  // for the close button
             { public void windowClosing(WindowEvent e) { f.dispose(); } }
          );
         c = f; isFrame = true;
       } // new window Frame !

      c.setLayout(new FlowLayout());

      Button b1 = new Button("++");                      // Button
      b1.addActionListener(
         new ActionListener()
          { public void actionPerformed(ActionEvent e)
             { Flexible.action1(); monitorState(); }
          } );
      c.add("a1", b1);

      Button b2 = new Button("--");                      // Button
      b2.addActionListener(
         new ActionListener()
          { public void actionPerformed(ActionEvent e)
             { Flexible.action2(); monitorState(); }
          } );
      c.add("a2", b2);

      stateDisplay = new Label("waiting");               // text Label
      c.add("sd", stateDisplay);

      this.c = c;

      if(isFrame)
       { ((Window)c).pack();  ((Window)c).setVisible(true); } //make it visible
    }//GUI constructor


   // GUI's typically display something of the state of the computation:
   public void monitorState()
    { stateDisplay.setText("s="+Flexible.s);
      c.repaint();  //repaint is a method of class Component
    }

 }//GUI class

// L. Allison 2007 http://www.allisons.org/ll/