public CalculatorPanel() { result = 0; lastCommand = "+"; ActionListener command = new CommandAction(); GridLayout layout = new GridLayout(2, 5); layout.setHgap(5); layout.setVgap(5); panel = new JPanel(); panel.setLayout(layout); panel.setPreferredSize(new Dimension(400, 200)); // add display display = new JTextField(); Command = new JTextField("+"); firstNumber = new JTextField(); secondNumber = new JTextField(); JTextField equal = new JTextField("="); equal.setEnabled(false); display.setEnabled(false); Command.setEnabled(false); panel.add(firstNumber); panel.add(Command); panel.add(secondNumber); panel.add(equal); panel.add(display); addButton("+", command); addButton("-", command); addButton("*", command); addButton("/", command); addButton("OK", command); add(panel, BorderLayout.CENTER); }