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.

Answer 1

// Shape2D.java

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

//end of Shape2D.java

// Rectangle2D.java

public class Rectangle2D extends Shape2D
{
// fields
private double length;
private double width;
  
// constructor
public Rectangle2D(double length, double width)
{
this.length = length;
this.width = width;
}

// overriden method to return the area of rectangle
@Override
public double get2DArea() {
return length*width;
}
  
}

//end of Rectangle2D.java

// Circle2D.java
public class Circle2D extends Shape2D
{
// field
private double radius;
  
// constructor
public Circle2D(double radius)
{
this.radius = radius;
}

// overriden method to return the area of circle
@Override
public double get2DArea() {
return Math.PI*Math.pow(radius, 2);
}
  
}

//end of Circle2D.java

// Shape2DDriver.java

public class Shape2DDriver {

// method that takes as input Shape2D object and displays the area of the object, rounded to one decimal place.
public static void displayName(Shape2D shape)
{
System.out.printf("Area: %.2f\n",shape.get2DArea());
}
  
public static void main(String[] args)
{
// test the class and methods
Shape2D shape = new Rectangle2D(12, 7);
displayName(shape);
shape = new Circle2D(5);
displayName(shape);
}
}

//end of Shape2DDriver.java

Output :

I have tried to explain it in very simple language and I hope that i have answered your question satisfactorily.Leave doubts in comment section if any.