Java – why can’t I access my panel’s getWidth () and getHeight () functions?

I'm writing a simple program to test the basic GUI The program prints a letter in the middle of the screen, allowing the user to move it using the arrow keys Everything is fine, but when I try to center the letter at the beginning of the program, it seems that the getWidth and getHeight functions do not return the correct number

This is a fragment containing my panel class

static class LinePanel extends JPanel{
    int xCenter = getWidth() /2;
    int yCenter = getHeight() /2;

    private int x = xCenter;
    private int y = yCenter;
    private char keyChar = 'A';

    public LinePanel(){
        addKeyListener(new KeyAdapter(){
            public void keyPressed(KeyEvent e) {
                switch (e.getKeyCode()) {
                    case KeyEvent.VK_DOWN: y += 10; break;
                    case KeyEvent.VK_UP: y -= 10; break;
                    case KeyEvent.VK_LEFT: x -= 10; break;
                    case KeyEvent.VK_RIGHT: x += 10; break;
                    default: keyChar = e.getKeyChar();
                }

                repaint();

            }
        });
    }

    protected void paintComponent(Graphics g){
        super.paintComponent(g);

        g.setFont(new Font("TimesRoman",Font.PLAIN,24));
        g.drawString(String.valueOf(keyChar),x,y);
    }
}

Why do my getWidth and getHeight functions return '0'?

Thanks for your help

Solution

I can't say why, but:

One way to avoid this is to override your getpreferredsize () function and return your preferred size