//
// "closeable frame" class, alternate implementation.  compare with
//      CloseableFrame.java.
//
import java.awt.* ;
import java.awt.event.* ;

//
// a CloseableFrameAlt object is a frame that listens for window events,
//      and processes "close" by disposing of the frame.
// this class has a static counter variable that keeps track of the
//      number of frames created and not closed.  when all have been 
//      closed, System.exit() is called to terminate the application.
//
public class CloseableFrameAlt extends Frame {

        static int framecount = 0 ;

        // zero-argument constructor for frame without title.
        public CloseableFrameAlt() {
                super() ;
                subConstruct() ;
        }

        // one-argument constructor for frame with title.
        public CloseableFrameAlt(String s) {
                super(s) ;
                subConstruct() ;
        }

        void subConstruct() {
                framecount++ ;
                // respond to window-close event and ignore other
                //      window events.
                addWindowListener(new WindowAdapter() {
                        // WindowAdapter defines "stub" methods for
                        //      all WindowListener methods.
                        public void windowClosing(WindowEvent wEvt) {
                                // get rid of frame and release
                                //      associated resources.
                                dispose() ;
                                framecount-- ;
                                if (framecount <= 0) 
                                        System.exit(0) ;
                        }
                } ) ;
        }
}