// TestInterface.java: Use the Comparable interface
// and the generic max method to find max objects
public class TestInterface {
  /** Main method */
  public static void main(String[] args) {
    // Create two comparable circles
    ComparableCircle circle1 = new ComparableCircle(5);
    ComparableCircle circle2 = new ComparableCircle(4);

    // Display the max circle
    Object circle = Max.max(circle1, circle2);
    System.out.println("The max circle's radius is " +
      ((Circle)circle).getRadius());
    System.out.println(circle);
  }
}

// ComparableCircle is a subclass of Circle, which implements the
// Comparable interface
class ComparableCircle extends Circle implements Comparable {
  /** Construct a ComparableCircle with a specified radius */
  public ComparableCircle(double r) {
    super(r);
  }

  /** Implement the compareTo method defined in Comparable */
  public int compareTo(Object o) {
    if (getRadius() > ((Circle)o).getRadius())
      return 1;
    else if (getRadius() < ((Circle)o).getRadius())
      return -1;
    else
      return 0;
  }
}

// Max.java: Find a maximum object
public class Max {
  /** Return the maximum between two objects */
  public static Object max(Object o1, Object o2) {
    if (((Comparable)o1).compareTo(o2) > 0)
      return o1;
    else
      return o2;
  }
}

public class Circle extends GeometricObject {
  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;
  }

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

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

  /** 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);
  }
}

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();
  }

  /** 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,
     so, the get method name is 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;
  }

  /** Return a string representation of this object */
  public String toString() {
    return "created on " + dateCreated + "\ncolor: " + color +
      " and filled: " + filled;
  }

  /** Abstract method getArea */
  public abstract double getArea();

  /** Abstract method getPerimeter */
  public abstract double getPerimeter();
}