Question

(Enable Rectangle comparable) Rewrite the Rectangle class in Listing 13.3 to extend GeometricObject and implement the Comparable interface. Override the equals method in the Object class. Two Rectangle objects are equal if their areas are the same. Draw the UML diagram that involves Rectangle, GeometricObject, and Comparable. Also include explain paragraph.

Answer 1

SOLUTION-

code -

Program code screen shot:

Program code:

Program code:

//define the GeometricObject of the abstract class

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 default geometric object with

     //color and filled value

     protected GeometricObject(String color, boolean filled)

     {

          dateCreated = new java.util.Date();

          this.color = color;

          this.filled = filled;

     }

     // Returns color

     public String getColor()

     {

          return color;

     }

     // assign a new color

     public void setColor(String color)

     {

          this.color = color;

     }

     // returns filled value

     public boolean isFilled()

     {

          return filled;

     }

     // Set a new filled value

     public void setFilled(boolean filled)

     {

          this.filled = filled;

     }

     // returns creation date

     public java.util.Date getDateCreated()

     {

          return dateCreated;

     }

     // returns string representation of object

     public String toString()

     {

          return "created on "+dateCreated+"\ncolor: "+color+" and filled: "+filled;

     }

     public abstract double getArea();

     public abstract double getPerimeter();

}

// Defines rectangle class

public class Rectangle extends GeometricObject

{

     public double width;

     public double height;

     // construct a rectangle

     public Rectangle(double width, double height)

     {

          this.width = width;

          this.height = height;

     }

     // method to find out perimeter

     public double getPerimeter()

     {

          return 2 * (width + height);

     }

     // method to find out area

     public double getArea()

     {

          return width * height;

     }

     // method to check equality

     public boolean equals(Object obj)

     {

          System.out.println(this.getArea()+" "+((Rectangle)obj).getArea());

          if(this.getArea() == ((Rectangle)obj).getArea())

              return true;

          return false;

     }

}

//Definition of the ComparableRectangle that implements the Comparable

//interface

public class ComparableRectangle extends Rectangle implements Comparable

{

     //constructor

     public ComparableRectangle(double width, double height)

     {

          super(width, height);

     }

     //overriding the compareTo method

     public int compareTo(Object o)

     {

          //logic to compare the Areas of the Rectangle objects

          if(getArea() > ((ComparableRectangle)o).getArea())

              return 1;

          else if(getArea()

                   < ((ComparableRectangle)o).getArea())

              return -1;

          else

              return 0;

     }

}

//definition of the TestEqualRectangle

public class TestEqualRectangle

{

     public static void main(String[] args)

     {

          //create objects of the Rectangle classes

          Rectangle cc = new Rectangle(6, 7);

          Rectangle cc1 = new Rectangle(8, 8);

          //call the equals function to compare the two

          //objects

          boolean res = cc.equals(cc1);

          //print the results

          System.out.println("Result: "+res);

     }

}

Sample Output:

42.0 64.0

Result: false

UML diagram:

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