public ClasseGrafica () {

		super("Mercadinho do Zé");

		setVisible(true);
		setSize(500, 500);
		setDefaultCloseOperation(this.EXIT_ON_CLOSE);
		center();

		painel = new JPanel();
		painel.setBorder(BorderFactory.createTitledBorder("Menu"));
		painel.setLayout(new GridBagLayout());
		painel.setSize(new Dimension(500, 500));

		GridBagConstraints grid = new GridBagConstraints();
		grid.insets = new Insets(4, 4, 4, 4);

		grid.gridx = 0;
		grid.gridy = 0;
		JLabel labelManterProdutos = new JLabel("Manter produtos");
		painel.add(labelManterProdutos, grid);

		grid.gridx = 1;
		grid.gridy = 0;		
		botaoOkManterProdutos = new JButton("OK");
		botaoOkManterProdutos.addActionListener(this);
		painel.add(botaoOkManterProdutos, grid);

		grid.gridx = 0;
		grid.gridy = 1;
		JLabel labelCadastrarVenda = new JLabel("Cadastrar venda");
		painel.add(labelCadastrarVenda, grid);

		grid.gridx = 1;
		grid.gridy = 1;		
		botaoOkCadastrarVenda = new JButton("OK");
		botaoOkCadastrarVenda.addActionListener(this);
		painel.add(botaoOkCadastrarVenda, grid);

		grid.gridx = 0;
		grid.gridy = 2;		
		JLabel labelConsultarVenda = new JLabel("Consultar venda");
		painel.add(labelConsultarVenda, grid);

		grid.gridx = 1;
		grid.gridy = 2;		
		botaoOkConsultarVenda = new JButton("OK");
		botaoOkConsultarVenda.addActionListener(this);
		painel.add(botaoOkConsultarVenda, grid);

		grid.gridx = 0;
		grid.gridy = 2;		
		JLabel labelSair = new JLabel("Consultar venda");
		painel.add(labelSair, grid);

		grid.gridx = 1;
		grid.gridy = 3;		
		botaoOkSair = new JButton("Sair");
		botaoOkSair.addActionListener(this);
		painel.add(botaoOkSair, grid);

		this.add(BorderLayout.BEFORE_FIRST_LINE, painel);

	}