(The Octagon class) Write a class named Octagon that extends GeometricObject and implements the Comparable and Cloneable interfaces. Assume that all eight sides of the octagon are of equal length. The area can be computed using the following formula:

/*********************************************************************************
* (The Octagon class) Write a class named Octagon that extends GeometricObject   *
* and implements the Comparable and Cloneable interfaces. Assume that all eight  *
* sides of the octagon are of equal length. The area can be computed using the   *
* following formula:                                                             *
*                                                                                *
*                      area = (2 + 4/√22)* side * side                           *
*                                                                                *
* Draw the UML diagram that involves Octagon, GeometricObject, Comparable, and   *
* Cloneable. Write a test program that creates an Octagon object with side value *
* 5 and displays its area and perimeter. Create a new object using the clone     *
* method and compare the two objects using the compareTo method.                 *
*********************************************************************************/
public class Exercise_13_11 {
	/** Method method */
	public static void main(String[] args) throws CloneNotSupportedException {
		// Create an Octagon object
		Octagon octagon1 = new Octagon(5);

		// Display area and perimeter of object
		System.out.println("\nOctagon:\nArea: " + octagon1.getArea() + 
			"\nPerimeter: " + octagon1.getPerimeter());

		// Create new object using the clone method
		System.out.println("Cloning Octagon...");
		Octagon octagon2 = (Octagon)octagon1.clone();

		// Compare the two object using compareTo method
		int result = (octagon1.compareTo(octagon2));
		if (result == 1)
			System.out.println("Octagon is greather than its clone.");
		else if (result == -1)
			System.out.println("Octagon is less than its clone."); 
		else
			System.out.println("Octagon is equal to its clone.");
	}
}

GeometricObject.java

public abstract class GeometricObject {
	private String color = "while";
	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;
	}

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

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

}

Octagon.java

public class Octagon extends GeometricObject 
		implements Cloneable, Comparable<Octagon> {
	private double side;

	public Octagon() {
	}

	/** Construct a Octagon of a specified side */
	public Octagon(double side) {
		this.side = side;
	}

	/** Set a new specified side */
	public void setSide(double side) {
		this.side = side;
	}

	/** Return side */
	public double getSide() {
		return side;
	}

	@Override /* Return the area of this Octagon */
	public double getArea() {
		return (2 + 4 / Math.sqrt(2)) * side * side;
	}

	@Override /* Return the perimeter of this Octagon */
	public double getPerimeter() {
		return 8 * side;
	}

	@Override /** Implement compareTo method */
	public int compareTo(Octagon o) {
		if (getArea() > o.getArea())
			return 1;
		else if (getArea() < o.getArea())
			return -1;
		else
			return 0;
	}

	@Override /** Override the protected clone in method defined
		in the Object class, and strengthen its accessiblity */
	public Object clone() throws CloneNotSupportedException {
		return super.clone();
	}

	@Override /** Retrun a String description of this Octagon object*/
	public String toString() {
		return super.toString() + "\nArea: " + getArea() + 
			"\nPerimeter: " + getPerimeter();
	}
}