Do I actually call the paintComponent method I make when creating a rectangle in Java?

Question

This is my current RectangleComponent class and I add it to a panel in my main JFrame but it never appears. I thought it wasn't drawing so I decided to call the paintComponent method in the Rectangle's constructor, and after sorting through 4-5 nullPointerExceptions, nothing has changed. I've read multiple guides on how to draw rectangles and I have seen multiple code examples, but I can never get the panels to work with more than one JComponent. If you could, please take a brief look at my code and see if you can devise a solution. Thank you for your time. Also listed is the Frame I call the rectangle constructor in.

public class GameFrame extends JFrame
{
    private SpellBarComponent bar;
    private JPanel mainPanel = new JPanel();
    private JPanel buttonPanel = new JPanel();
    private JPanel healthPanel = new JPanel();
    Color green = new Color(29, 180, 29);
    Color red = new Color(255, 0, 0);
    private RectangleComponent life;
    private RectangleComponent death;
    private JFrame frame = new JFrame();

    public GameFrame(char x)
    {
        frame.setSize(1024, 768);
        frame.setTitle("Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        FlowLayout layout = new FlowLayout();
        createPanels(x);
        healthPanel.setLayout(layout);
        buttonPanel.setLayout(layout);
        mainPanel.setLayout(layout);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        repaint();
    }

    public RectangleComponent getLife()
    {
        return life;
    }

    private void createHealth()
    {
        life = new RectangleComponent(green, healthPanel);
        death = new RectangleComponent(red, healthPanel);
    }

    private void createPanels(char x)
    {
        add(healthPanel);
        pack();
        createBar(x);
        createHealth();
        mainPanel.add(buttonPanel);
        mainPanel.add(healthPanel);
        healthPanel.add(death);
        healthPanel.add(life);
        buttonPanel.add(bar.getSpell1());
        buttonPanel.add(bar.getSpell2());
        buttonPanel.add(bar.getSpell3());
        add(mainPanel);
    }

    private void createBar(char x)
    {
        bar = new SpellBarComponent(x, mainPanel);
    }
}


public class RectangleComponent extends JComponent
{
    Color color;
    int width;
    int height = 18;
    RoundRectangle2D roundedRectangle;
    private JPanel panel;
    public RectangleComponent(Color color, JPanel panel)
    {
        this.panel = panel;
        this.color = color;
        paintComponent(panel.getGraphics());
    }

    public void paintComponent(Graphics g)
    {
        Graphics2D graphics2 = (Graphics2D) g;
        width = 125;
        roundedRectangle = new RoundRectangle2D.Float(10, 10, width, height, 10, 10);
        graphics2.setPaint(color);
        graphics2.fill(roundedRectangle);
        graphics2.draw(roundedRectangle); 
    }

    public void subtractLife(int amount)
    {
        width -= amount;
        roundedRectangle.setRoundRect(10, 10, width, height, 10, 10);
        repaint();
    }
}

Answer 1

No need to pass JPanel to the constructor of RectangleComponent just to get Graphics, and no need to manually call paintComponent. See Painting in AWT and Swing. Check out this example that demonstrates a custom component that paints a rectangle.