public abstract class EquidistantShape {
   private double theRadius;

   public void setRadius(double newRadius) {
      if (newRadius >= 0.0) {
         theRadius = newRadius;
      } // end if
   } // end setRadius

   public double radius() {
      return theRadius;
   } // end radius

   public abstract void displayStatistics();
} // end EquidistantShape