Concentric circles using a random center point

I am doing a problem I found online for practice and I am having trouble figuring out a step. My goal is to print 6 concentric circles with random colors while using an array as the diameter.

I have managed to get everything working except my circles are not concentric and seem to just draw away from each other.

Any ideas?

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;
import java.awt.*;
import java.util.Random;


public class E3 {

    public static int [] diameters = new int[6];


    public static void main(String[] args) 
        throws FileNotFoundException {
        Scanner console = new Scanner(new File("Practice47.txt"));

        int panelX = 400, panelY = 400;
        DrawingPanel panel = new DrawingPanel(panelX, panelY);
        panel.setBackground(Color.WHITE);
        Graphics g = panel.getGraphics();
        Random r = new Random();
        int xCenter=r.nextInt(400);
        int yCenter=r.nextInt(400);

      for(int i=0;i<diameters.length;i++){
          diameters[i]=console.nextInt();
          g.setColor(new Color(r.nextInt(256),r.nextInt(256), r.nextInt(256)));
            g.fillOval(xCenter, yCenter, diameters[i], diameters[i]);

        }

        for (int i=0;i<diameters.length;i++)
        System.out.println("diameters["+i+"] = "+ diameters[i]);


    }

    }

Here's what my output looks like: