//
// another example of the Java AWT, showing use of adapter classes.
//      (here, they're implemented as named inner classes.)
// see class definition for details.
//
import java.awt.* ;
import java.awt.event.* ;

//
// a PowerOf2 object represents an integer power of 2.
//
class PowerOf2 {

        int p = 0 ;

        void doubleIt() {
                p++ ;
        }

        void halveIt() {
                p-- ;
        }

        double val() {
                return Math.pow(2.0, (double) p) ;
        }

}

//
// a PowerOf2GUI object is a CloseableFrame with GUIs for two
//      PowerOf2 objects, each GUI consisting of two buttons to
//      invoke the doubleIt() and halveIt() methods and a display
//      area.
//
class PowerOf2GUI extends CloseableFrame {

        PowerOf2GUI() {

                super("Powerof2GUI") ;

                int num = 2 ;           // number of PowerOf2 objects

                setLayout(new GridLayout(num, 3, 20, 20) ) ;

                for (int i = 0 ; i < num ; i++) {

                        PowerOf2 obj = new PowerOf2() ;

                        // create buttons and add to frame.
                        Button h = new Button("halve it") ;
                        h.setActionCommand("halveIt") ;
                        add(h) ;
                        Button d = new Button("double it") ;
                        d.setActionCommand("doubleIt") ;
                        add(d) ;
                        
                        // create label (to display obj's value) and
                        //      add to frame.
                        Label lbl = new Label(
                                Double.toString(obj.val()),
                                Label.RIGHT) ;
                        add(lbl) ;

                        // create adapter objects and register as
                        //      listeners.
                        h.addActionListener(new Adapter(obj, lbl) ) ;
                        d.addActionListener(new Adapter(obj, lbl) ) ;
                }

                // set minimum size needed to hold everything, and
                //      display.
                pack() ;
                show() ;
        }

        //
        // ---- main ---------------------------------------------------
        //
        // no command-line arguments.
        //
        public static void main(String[] args) {

                PowerOf2GUI f = new PowerOf2GUI() ;

        }

        //
        // ---- inner class --------------------------------------------
        //
        // a Adapter object is an ActionListener that will be
        //      associated with a Button, a Label, and a PowerOf2 
        //      object.  it processes button-press events from the 
        //      Button by invoking doubleIt() or halveIt() (depending 
        //      on the Button's ActionCommand) on the PowerOf2 object 
        //      and displaying the resulting value in the Label.
        //
        class Adapter implements ActionListener {
        
                PowerOf2 obj ;
                Label l ;
        
                Adapter(PowerOf2 obj, Label l) {
                        this.obj = obj ;
                        this.l = l ;
                }
        
                public void actionPerformed(ActionEvent e) {
                        String s = e.getActionCommand() ;
                        if (s.equals("doubleIt")) {
                                obj.doubleIt() ;
                        }
                        else if (s.equals("halveIt")) {
                                obj.halveIt() ;
                        }
                        l.setText(Double.toString(obj.val())) ;
                }
        }
}