The Big Programming Thread - Page 263

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Point2D;

/**
   This class implements a Circle. It includes a method to test whether 
   two circles intersect.
*/
public class Circle
{
   private double xCenter;
   private double yCenter;
   private double radius;
   private Color color;

   /**
      Constructs a black circle.
      @param x the x-coordinate of the center
      @param y the y-coordinate of the center
      @param r the radius
   */
   public Circle(double x, double y, double r)
   {
      xCenter = x;
      yCenter = y;
      radius = r;
      color = Color.BLACK;
   }
   
   /**
      Sets the color of this circle.
      @param aColor the color
   */
   public void setColor(Color aColor)
   {
      color = aColor;
   }

   /**
      Draws the circles.
      @param g2 the graphics context
   */
   public void draw(Graphics2D g2)
   {
      if (radius < 0)
         return;

      g2.setColor(color);
      // draw the circle
      Ellipse2D.Double circle
         = new Ellipse2D.Double(xCenter - radius, yCenter - radius,
            2 * radius, 2 * radius);
      g2.draw(circle);
   }

   /**
      Tests whether or not the two circles intersect with each other.
      @param other the other circle
      @return true the two circles intersect
   */
   public boolean intersects(Circle other)
   {
           
          double distance;
          distance =......
           radius = radius + other.radius;
          if (distance <= radius)
          {
              return true;
            }
            else
            {
                return false;

            }
   }
}

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Point2D;
import javax.swing.JComponent;
import javax.swing.JPanel;

/**
   Shows two Circles and tests whether they intersect or not.
 */
public class CircleComponent extends JComponent
{
   private Circle circle1;
   private Circle circle2;

 
   /**
      Constructs a component for showing two circles.
      @param r1 the radius of the first circle
      @param r2 the radius of the second circle
   */
   public CircleComponent( double r1, double r2)
   {
      String message;

      circle1 = new Circle(100, 200, r1);
      circle2 = new Circle(200, 100, r2);
      Color color;
      if (........)
         color = Color.GREEN;
      else
         color = Color.RED;
      circle1.setColor(color);
      circle2.setColor(color);
   }

   public void paintComponent(Graphics g)
   {
      Graphics2D g2 = (Graphics2D) g;

      circle1.draw(g2);
      circle2.draw(g2);
   }
}