public final void initUI() {

		JPanel panel = new JPanel();

		panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
		panel.setLayout(new GridLayout(5, 4, 5, 5));

		String[] buttons = {
				"Cls", "Bck", "", "Close", "7", "8", "9", "/", "4",
				"5", "6", "*", "1", "2", "3", "-", "0", ".", "=", "+"
		};

		for (int i = 0; i < buttons.length; i++) {
			if (i == 2) {
				panel.add(new JLabel(buttons[i]));
			} else {
				panel.add(new JButton(buttons[i]));
			}
		}

		add(panel);

		setTitle("GridLayout");
		setSize(350, 300);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setLocationRelativeTo(null);
	}