Layout Management and GUI Components - Learning Java Through Games - page 274

public static void main(String [] args) throws Exception {
CalculatorFrame f = new CalculatorFrame() ;
f . setVisible( true );

}

}

class CalculatorFrame extends JFrame {
JTextField text = new JTextField(20) ;

public CalculatorFrame() throws Exception {
setDefaultCloseOperation(JFrame.DISPOSEON CLOSE) ;
JPanel displayPanel = new JPanel () ;
JPanel buttonPanel = new JPanel () ;
JPanel bottomPanel = new JPanel () ;

displayPanel .add(text) ;
String [] buttonNames = { "7" , "8" , "9" , "+" , "4" , "5" , "6" , "-" , "1"
, "2" , "3" , "*" , "0" , "(" , ")" , "/" } ;
buttonPanel . setLayout( new GridLayout (4 , 4 , 5 , 5) ) ;
for (String el : buttonNames) {
buttonPanel .add( new CalculatorButton( el )) ;
JButton evaluateButton = new JButton( "EVALUATE" );
JButton clearButton = new JButton( "CLEAR" );
clearButton . addActionListener( new ActionListener ()

{

public void actionPerformed(ActionEvent e) {

text . setText( "" );

}
} );
evaluateButton . addActionListener( new ActionListener () {

public void actionPerformed(ActionEvent e) {

try {
String s = ( new ScriptEngineManager () .getEngineByName( "
JavaScript" ) . eval(text .getText() .trim())) . toString() ;
text . setText(s) ;

}

catch (Exception exc) {
text . setText( "" );

}

}

} );

bottomPanel . add( new CalculatorButton( "." ));
bottomPanel . add( clearButton ) ;
bottomPanel . add( evaluateButton) ;

add(displayPanel , BorderLayout .NORTH) ;
add(buttonPanel , BorderLayout .CENTER) ;
add(bottomPanel , BorderLayout .SOUTH) ;
setResizable( false );
pack() ;

}

private class CalculatorButton extends JButton {

public CalculatorButton(String name) {

super (name) ;