How do I draw an alphabet inside a painted circle with random size and random coordinates?

The title says it all.

I have a class which extends JPanel. The size of the JPanel is set by adding the below method in the class:

@Override
public Dimension getPreferredSize() {
    return new Dimension(WIDTH, HEIGHT);
}

the relevant fields of this class are:

int position = 0;

int randomSize = 0; 
int randomPositionX = 0;
int randomPositionY = 0;

public final static int MAX_SIZE = 100;
public final static int MIN_SIZE = 10;

public final static int WIDTH    = 500;
public final static int HEIGHT   = 500;

private Random rand = new Random();

String alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

I choose a random size (Maximum of 100 and minimum of 10) and a random coordinate from a method. I also choose a random index for the string alphabets:

randomSize = MIN_SIZE + (rand.nextInt(MAX_SIZE - MIN_SIZE) + 1);

randomPositionX = rand.nextInt(WIDTH - randomSize);
randomPositionY = rand.nextInt(HEIGHT - randomSize);

position = rand.nextInt(alphabets.length());

My attempt at drawing the alphabet and circle:

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g); 
    g.fillOval(randomPositionX, randomPositionY, randomSize, randomSize);
    g.setFont(new Font("TimesRoman", Font.PLAIN, randomSize));
    g.setColor(Color.RED);
    g.drawString(alphabets.charAt(position) + "", randomPositionX + (randomSize/2), randomPositionY + (randomSize/2));
}

But it doesn't draw the alphabet at the center of the circle. In short, the problematic line is

g.drawString(alphabets.charAt(position) + "", randomPositionX + (randomSize/2), randomPositionY + (randomSize/2));

How do I achieve what I want?