public class Circle extends GeometricObject {
  //inherits from superclass GeometricObject: 
  //  methods: getColor setColor isFilled setFilled getDateCreated toString
  //  Can not directly access inherited 'color' 'filled' 'dateCreated' fields
  //  because they are private in superclass.
  private double radius;

  public Circle() {
    //compiler inserts: super();  //call of superclass' 0-arg constructor
  }

  public Circle(double radius) {
    //compiler inserts: super();
    this.radius = radius;
  }

  public double getRadius() {
    return radius;
  }

  public void setRadius(double radius) {
    this.radius = radius;
  }

  public double getArea() {
    return radius * radius * Math.PI;
  }
  
  public double getDiameter() {
    return 2 * radius;
  }
  
  public double getPerimeter() {
    return 2 * radius * Math.PI;
  }

  public void printCircle() {
    System.out.println("The circle is created " + getDateCreated() +
      " and the radius is " + radius);
  }
}