/*************************************************************
 *  Compilation:  javac Ball.java
 *  Execution:    java Ball
 *  Dependencies: StdDraw.java
 *
 *  Object oriented implementation of a 2-d Ball, Booksite 3.4 
 *************************************************************/

public class Ball {

   // declare instance variables
   _____________________________________________   // position
   _____________________________________________   // velocity
   _____________________________________________   // radius

   // constructor
   public Ball() {
      // Always start ball position at (0, 0)



      // Initial velocity and size generated randomly




   }

   // move the ball one step
   public void move() {
      // Bounce off border walls



      // update position using unit change in time



   }

   // draw the ball
   public void draw() {


   }

   // test client: This part is complete.
   public static void main(String[] args) {
      // create and initialize two balls
      Ball b1 = new Ball();
      Ball b2 = new Ball();

      // animate them
      StdDraw.setXscale(-1.0, +1.0);
      StdDraw.setYscale(-1.0, +1.0);
      while (true) {
         StdDraw.setPenColor(StdDraw.GRAY);
         StdDraw.filledSquare(0.0, 0.0, 1.0);
         StdDraw.setPenColor(StdDraw.BLACK);
         b1.move();
         b2.move();
         b1.draw();
         b2.draw();
         StdDraw.show(20);
      }
   }
}