I used the answer on this question.
The code I used looks something like this:
/**
* Draw a String centered in the middle of a Rectangle.
*
* @param g The Graphics instance.
* @param text The String to draw.
* @param rect The Rectangle to center the text in.
*/
public void drawCenteredString(Graphics g, String text, Rectangle rect, Font font) {
// Get the FontMetrics
FontMetrics metrics = g.getFontMetrics(font);
// Determine the X coordinate for the text
int x = rect.x + (rect.width - metrics.stringWidth(text)) / 2;
// Determine the Y coordinate for the text (note we add the ascent, as in java 2d 0 is top of the screen)
int y = rect.y + ((rect.height - metrics.getHeight()) / 2) + metrics.getAscent();
// Set the font
g.setFont(font);
// Draw the String
g.drawString(text, x, y);
}