Question

Shapes2D

Write the following four classes to practice using an abstract class and polymorphism. Submit all four classes.

Shape2D class

For this class, include just an abstract method name get2DArea() that returns a double.

Rectangle2D class

Make this class inherit from the Shape2D class. Have it store a length and a width as fields. Provide a constructor that takes two double arguments and uses them to set the fields. Note, the area of a rectangle is the length times the width.

Circle2D class

Also make this class inherit from the Shape2D class. Have it store a radius as a field. Provide a constructor that takes a double argument and uses it to set the field. Note, the area of a circle is PI times it's radius times it's radius.

Shape2DDriver class

Have this class provide a method named displayName() that takes an object from just any of the above three classes (you can't use an Object type parameter). Have the method display the area of the object, rounded to one decimal place.

Written in java

Answer 1

abstract class Shape2D
{
public abstract double get2DArea();
}

class Rectangle2D extends Shape2D
{
   private double length,width;
  
public Rectangle2D(double length,double width)
{
   this.length = length;
   this.width = width;
}
public double get2DArea()
{
   return length*width;
}
}

class Circle2D extends Shape2D
{
private double radius;
  
public Circle2D(double radius)
{
   this.radius = radius;
}
public double get2DArea()
{
   return Math.PI*radius*radius;
}
}

class Shape2DDriver
{
   public static void main (String[] args)
   {
   Rectangle2D r = new Rectangle2D(5.5,6.5);
   display(r);
     
   Circle2D c = new Circle2D(4.0);
   display(c);

   }
   public static void display(Shape2D obj)
   {
       System.out.printf("\narea = %.1f",obj.get2DArea());
   }
}

Output:

area = 35.8
area = 50.3

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