// Fig. 7.5: Circle.java
// Definition of class Circle
public class Circle extends Point {  // inherits from Point
   protected double radius;

   // no-argument constructor
   public Circle()
   {
      // implicit call to superclass constructor here
      setRadius( 0 );        
      System.out.println( "Circle constructor: " +
                          toString() );
   }

   // Constructor
   public Circle( double r, int a, int b )
   {
      super( a, b );  // call the superclass constructor
      setRadius( r );  
      System.out.println( "Circle constructor: " +
                          toString() );
   }

   // finalizer
   protected void finalize() throws Throwable
   {
      System.out.println( "Circle finalizer: " + 
                          toString() );
      super.finalize();  // call superclass finalize method
   }

   // Set radius of Circle
   public void setRadius( double r ) 
      { radius = ( r >= 0 ? r : 0 ); }

   // Get radius of Circle
   public double getRadius() { return radius; }

   // Calculate area of Circle
   public double area()
      { return Math.PI * radius * radius; }

   // convert the Circle to a String
   public String toString()
   {
      return "Center = " + super.toString() +
             "; Radius = " + radius;
   }
}