//一个几何接口
interface GeometricInterface {
    double getArea();
    double getPerimeter();
}

//一个几何对象
public abstract class GeometricObject {
  private String color = "white";
  private boolean filled;
  private java.util.Date dateCreated;

  /** Construct a default geometric object */
  protected GeometricObject() {
    dateCreated = new java.util.Date();
  }

  /** Construct a geometric object with color and filled value */
  protected GeometricObject(String color, boolean filled) {
    dateCreated = new java.util.Date();
    this.color = color;
    this.filled = filled;
  }

  /** Return color */
  public String getColor() {
    return color;
  }

  /** Set a new color */
  public void setColor(String color) {
    this.color = color;
  }

  /** Return filled. Since filled is boolean,
   *  the get method is named isFilled */
  public boolean isFilled() {
    return filled;
  }

  /** Set a new filled */
  public void setFilled(boolean filled) {
    this.filled = filled;
  }

  /** Get dateCreated */
  public java.util.Date getDateCreated() {
    return dateCreated;
  }

  @Override
  public String toString() {
    return "created on " + dateCreated + "\ncolor: " + color +
      " and filled: " + filled;
  }
 
}

//一个矩形类，继承GeometricObject 类，实现GeometricInterface 接口
public class Rectangle extends GeometricObject   implements GeometricInterface {
  private double width;
  private double height;

  public Rectangle() {
  }

  public Rectangle(double width, double height) {
    this.width = width;
    this.height = height;
  }

  /** Return width */
  public double getWidth() {
    return width;
  }

  /** Set a new width */
  public void setWidth(double width) {
    this.width = width;
  }

  /** Return height */
  public double getHeight() {
    return height;
  }

  /** Set a new height */
  public void setHeight(double height) {
    this.height = height;
  }

 @Override /** Return area */
  public double getArea() {
    return width * height;
  }

 @Override /** Return perimeter */
  public double getPerimeter() {
    return 2 * (width + height);
  }
}

//一个圆类，继承GeometricObject 类，实现GeometricInterface 接口
public class Circle extends GeometricObject  implements GeometricInterface {
  private double radius;

  public Circle() {
  }

  public Circle(double radius) {
    this.radius = radius;
  }

  /** Return radius */
  public double getRadius() {
    return radius;
  }

  /** Set a new radius */
  public void setRadius(double radius) {
    this.radius = radius;
  }

 @Override /** Return area */
  public double getArea() {
    return radius * radius * Math.PI;
  }

  /** Return diameter */
  public double getDiameter() {
    return 2 * radius;
  }

 @Override /** Return perimeter */
  public double getPerimeter() {
    return 2 * radius * Math.PI;
  }

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