JButton not displaying

Question

Hi does anyone know why my "button1" is not displaying? I can not seem to figure it out when I execute the program it all works and runs successfully but it does not display this button. Any help would be appreciated thanks.

private Container c;
private JPanel gridPanel;
private JComboBox combo;
final JLabel label = new JLabel();
private JButton button1 = new JButton("Clear");
private JButton button2 = new JButton("Exit");

/**
 * Christopher Haddad - 559815X
 */
public Planets() {
    c = getContentPane();
    gridPanel = new JPanel();
    gridPanel.setLayout(new GridLayout(5, 0, 0, 0));

    label.setVisible(true);

    combo = new JComboBox(); 
    combo.setEditable(false);
    combo.addItem("No Planet Selected");
    combo.addItem("Mercury"); 
    combo.addItem("Venus"); 
    combo.addItem("Earth"); 
    gridPanel.add(combo);

    add(button1);
    add(button2);
    button1.addActionListener(this);
    button2.addActionListener(this);

    c.add(gridPanel, BorderLayout.NORTH);
    setTitle("Planet Diameter"); 
    setSize(700, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);

    combo.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            JComboBox comboBox = (JComboBox) event.getSource();

            Object select = comboBox.getSelectedItem();

            if(select.toString().equals("No Planet Selected"))
                label.setText("");
            else if(select.toString().equals("Mercury"))
                label.setText("The planet Mercury is 3100kms in diameter");
            else if(select.toString().equals("Venus"))
                label.setText("The planet Venus is 7500kms in diameter");
            else if (select.toString().equals("Earth"))
                label.setText("The planet Earth is 8000kms in diameter");

        }
    });
    getContentPane().add(combo);
    getContentPane().add(label);
}

    // event handling method, implementing the actionPerformed method of ActionListener 
    public void actionPerformed(ActionEvent e) 
    { 
        // set the button label to number of times it has been clicked
        if(e.getSource() == button1) {
            label.setText(" ");
        }
        else if(e.getSource() == button2) {
            System.exit(0);
        }
    } 

Answer 1

It is difficult to be sure, but I assume you are adding content directly to a top level container, like a JFrame

JFrame uses a BorderLayout as it's default layout manager, so using

add(button1);
add(button2);

Basially says, add button1 to the CENTER position then add button2 to the CENTER position. BorderLayout will only allow a single component to exist at a specific location.

Try adding the buttons to another panel first...