JFrame
Class JavaCalcFrame extends Jframe
//constructor for menu etc
:
// misc events handling, e.g.:
    addWindowListener(new WindowAdapter(){
     public void windowClosing(WindowEvent e){
       System.exit(0);
     }
   });
:
//Instantiate main panel
Container contentpane = getContentPane();
CalculatorPanel panel = new CalculatorPanel();
contentPane.add(panel);