// Class GUIcircles
import java.awt.Graphics;
import javax.swing.JPanel;

public class GUIcircles extends JPanel
{
private int number;

public GUIcircles( int numberOfCircles)
{
number = numberOfCircles;
}

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

int width = getWidth(), height = getHeight();

for( int radius=10; radius<=number*radius; radius+=10)
g.drawOval( width/2-radius, height/2-radius, radius*2, radius*2);
}
}

//Class GUIcirclesTest
import javax.swing.JFrame;
import javax.swing.JOptionPane;
public class GUIcirclesTest {
public static void main( String[] args )
{
String input = JOptionPane.showInputDialog("Enter number of circles to draw");
int number = Integer.parseInt( input );
// Create a panel that contains our drawing
GUIcircles panel = new GUIcircles(number);

// Create a new frame to hold the panel
JFrame application = new JFrame();

// Set the frame to exit when it is closed
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

application.add( panel ); // Add the panel to the frame
application.setSize( 250, 250); // Set the size of the frame
application.setVisible( true ); // Make the frame visible
}
}