Question

IN JAVA

For the following questions, “define a class” means the following:

• Create an appropriately-named file containing the Java class definition, including the following:

– A block comment describing the file (and hence the class), as always

– Any instance variables, as required by the question

– Accessor (getter) and mutator (setter) methods for any instance variables

– Constructors as appropriate or as required by the question

– A toString method that prints instances of the class informatively

– Any additional methods as required by the question. All methods other than getters and setters MUST have a descriptive comment before their definition.

• Create a separate appropriately-named file containing a different Java class with a main method that tests your new class by doing the following:

– Create at least two instances of the class.

– Change at least one of them using the class’ methods.

– Print all the objects informatively

Document how to run your code and interpret the output in your README.txt file.

1. Define the following class hierarchy for shapes:

(a) Define an abstract class Shape. Shapes have a color (which can be a string for now) and a boolean indicating whether or not they are filled. These should be properly encapsulated.

(b) Define an abstract class Shape2D that extends Shape. This class should define the abstract method getArea() that returns the area of a a Shape2D.

(c) Define a class Rectangle that extends Shape2D. A rectangle has a height and a width. Implement the getArea() method appropriately. Use the @Override annotation.

(d) Define a class Square that extends Rectangle. The class should have an appropriate constructor and also override setter methods as approrpiate to preserve “squareness.”

(e) Define a class Ellipse that extends Shape2D. An ellipse has a semi-major axis a and a semi-minor axis b (look it up if needed). The area of an ellipse is A = πab.

(f) Define a class Circle that extends Ellipse. You need appropriate contructor(s) and setter(s) for the class.

Illustrate all of these with a main method in a separate test class.

Answer 1

abstract class Shape
{
private String color;
private boolean filled;

public Shape(String color,boolean filled) // constructor
{
    this.color = color;
    this.filled = filled;
}

}

abstract class Shape2D extends Shape
{

public Shape2D(String color,boolean filled)
{
   super(color,filled); // call to base class constructor
}
public abstract double getArea();
}

class Rectangle extends Shape2D
{
   private double height,width;
  
   public Rectangle(String color,boolean filled,double height,double width)
   {
       super(color,filled);
       this.height = height;
       this.width = width;
   }
   public double getArea()
   {
   return height*width;
   }
  
}
class Square extends Rectangle
{
private double side;

public Square(String color,boolean filled,double side)
{
super(color,filled,side,side);
}

}
class Ellipse extends Shape2D
{
   private double axisA,axisB;
  
   public Ellipse(String color,boolean filled,double axisA,double axisB)
   {
       super(color,filled);
       this.axisA = axisA;
       this.axisB = axisB;
   }
   public double getArea()
   {
   return 3.14*axisA*axisB;
   }
  
}
class Circle extends Ellipse
{
private double radius;
public Circle(String color,boolean filled,double radius)
{
super(color,filled,radius,radius);
}
public double getRadius()
{
return radius;
}

}

  
class TestShapes
{
public static void main (String[] args)
{
    Rectangle r = new Rectangle("blue",true,3.5,5.4);
    System.out.println("\nArea of rectangle : "+r.getArea());
   
   Square s = new Square("red",false,4.5);
System.out.println("\nArea of square : "+s.getArea());
  
Ellipse e = new Ellipse("yellow",true,3.8,4.1);
System.out.println("\nArea of circle : "+e.getArea());
  
Circle c = new Circle("pink",true,4.9);
System.out.println("\nArea of circle : "+c.getArea());

  
  

  
}
}

Output:

Area of rectangle : 18.900000000000002

Area of square : 20.25

Area of circle : 48.9212

Area of circle : 75.3914

Do ask if any doubt. Please upvote.