/**
 * Concrete strategy to compute the area of a rectangular shape: knows its own width
 * and height and how to compute its area.

 * @author Dung X. Nguyen
 * <p>
 * Copyright 1999 by Dung X. Nguyen - Al rights reserved.
 */
public class Rectangle extends AShape
{
   private double _height;
   private double _width;

	/**
	 * Initializes this <code>Rectangle</code> width a given width and a given height

    * @param width width of this <code>Rectangle</code>, >= 0.
	 * @param height height of this <code>Rectangle</code>, >= 0.
    * @exception IllegalArgumentException, if params do not satisfy preconditions.
	 */
	public Rectangle(double width, double height)
	{
      if (width < 0 || height < 0)
      {
         throw new IllegalArgumentException ("Rectangle.Rectangle (width, height): width < 0) or height <0.");
      }
      _height  = height;
      _width   = width;
	}

   /**
   *  @returns this <code>Rectangle</code>'s area.
   */
   public double getArea()
   {
      return _height * _width;
   }

   /**
   * @returns a String describing a Rectangle with its width and height.
   */
   public String toString ()
   {
      return "Rectangle (width = " + _width + ", heigth = " + _height + ")";
   }
}