public class Circle
{
   // Represents a circle with center
   // at the point (centerX, centerY)
   // and with the specified radius

   private double centerX;
   private double centerY;
   private double radius;

   public Circle(double x, double y, double r) {
      centerX = x;
      centerY = y;
      radius = r;
   }

   public Circle(double r) {
      centerX = 0;
      centerY = 0;
      radius = r;
   }

   public Circle() {
      centerX = 0;
      centerY = 0;
      radius = 1d;
   }
	
   // area() returns the area of the circle
   public double area() {
      double area = Math.PI * radius * radius;
      return area;
   }

   // scale() enlarges/shrinks this circle
   public void scale(double factor) {
      radius = radius * factor;
   }

   // bigger() returns the circle with the largest area
   public Circle bigger(Circle other) {
      if (this.area() > other.area())
         return this;
      else
         return other;
   }

   // the mystery method does something unclear
   // Hint: in circles r2 = x2 + y2
   public boolean mystery(double x, double y) {
      double z = (x-centerX)*(x-centerX);
      z = z + (y-centerY)*(y-centerY);
      return (z < radius*radius);
   }
}