Position circles down the diagonal so that their borders

import java.awt.*;
import java.applet.Applet;

/** Position circles down the diagonal so that their borders
 *  just touch. Illustrates that AWT components are 
 *  rectangular and opaque.
  */

public class CircleTest2 extends Applet {
  public void init() {
    setBackground(Color.lightGray);
    setLayout(null); // Turn off layout manager.
    Circle circle;
    int radius = getSize().width/6;
    int deltaX = round(2.0 * (double)radius / Math.sqrt(2.0));
    for (int x=radius; x<6*radius; x=x+deltaX) {
      circle = new Circle(Color.black, radius);
      add(circle);
      circle.setCenter(x, x);
    }
  }

  private int round(double num) {
    return((int)Math.round(num));
  }
}
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Circle.java
*********************************
import java.awt.*;

/** A Circle component built using a Canvas. 
 *
  */

public class Circle extends Canvas {
  private int width, height;        
        
  public Circle(Color foreground, int radius) {
    setForeground(foreground);
    width = 2*radius;
    height = 2*radius;
    setSize(width, height);
  }

  public void paint(Graphics g) {
    g.fillOval(0, 0, width, height);
  }

  public void setCenter(int x, int y) {
    setLocation(x - width/2, y - height/2);
  }
}
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