         // quick phase
         //
         for (int i = 1 ; i <= 30 ; i++) {
            while ( buf.isFull() ) {
               label.setText("Buffer full") ;
               Thread.sleep(100) ;
            }

            n = prg.nextInt(100) ; // random number < 100
            buf.add(n) ;
            label.setText("Added " + n) ;
            Thread.sleep(500) ;
         }
