import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import javax.swing.JComponent;

/**
   A component that computes and draws the intersection points
   of a circle and a line.
*/
public class IntersectionComponent extends JComponent
{  
   /**
      Constructs the component from a given x-value for the line 
      @param anX  the x-value for the line (between 0 and 200)
   */
   public IntersectionComponent(double anX)
   {  
      x = anX;
   }
   
   public void paintComponent(Graphics g)
   {  
      Graphics2D g2 = (Graphics2D) g;

      // Draw the circle

      final double RADIUS = 100;

      Ellipse2D.Double circle 
            = new Ellipse2D.Double(0, 0, 2 * RADIUS, 2 * RADIUS);
      g2.draw(circle);
      
      // Draw the vertical line

      Line2D.Double line
            = new Line2D.Double(x, 0, x, 2 * RADIUS);
      g2.draw(line);
      
      // Compute the intersection points
      
      double a = RADIUS;
      double b = RADIUS;

      double root = Math.sqrt(RADIUS * RADIUS - (x - a) * (x - a));
      double y1 = b + root;
      double y2 = b - root;
      
      // Draw the intersection points

      LabeledPoint p1 = new LabeledPoint(x, y1);
      LabeledPoint p2 = new LabeledPoint(x, y2);
      
      p1.draw(g2);
      p2.draw(g2);
   }

   private double x;
}