Question

Design and implement class Circle to represent a circle object. The class defines the following attributes (variables) and methods:

1.      A private variable of type double named radius to represent the radius. Set to 1.

2.      Constructor Methods:

•        Python : An overloaded constructor method to create a default circle.

•        C# & Java: Default Constructor with no arguments.

•        C# & Java: Constructor method that creates a circle with user-specified radius.

3.      Method getRadius() that returns the radius.

4.      Method setRadius() that sets the radius.

5.      Method getArea() that returns the area.

6.      Method getCircumference() that returns the circumference.

7.      Method To String,

•        Java: toString()

•        C#: ToString()

•        Python: __str__(self)

that prints out a meaningful description of the circle as follows:

The circle has radius X.     Where X is the value of variable radius.

Now design and implement a test program to create a default circle object and test all class methods on the object. Print the object after each method call and use meaningful label for each method call as shown in the following sample run.

Sample run:

Print radius:

The radius is 1.

Print area:

The area is 3.14

Print circumference:

The perimeter is 6.28

Set radius to 10 and print the object: The circle has radius 10.

Print area:

The area is 314.23

Print circumference:

The perimeter is 62.81

Answer 1

Below is the java code with attached output as per required in given question. Please refer the comments given above variabe and method to better understand.

=================== TestCircle.java ========================

public class TestCircle {

public static void main(String[] args) {

Circle circle = new Circle();

System.out.println("Print radius: ");

System.out.println("The radius is " + circle.getRadius());

System.out.println("Print Area: ");

System.out.println("The area is " + circle.getArea());

System.out.println("Print Circumference: ");

System.out.println("The circumference is " + circle.getCircumference());

System.out.println("Calling toString(): ");

// Calling toString() method

System.out.println(circle);

System.out.println();

System.out.println("************** Setting Radius to 10 ************");

// Setting radius to 10

circle.setRadius(10);

System.out.println("Print radius: ");

System.out.println("The radius is " + circle.getRadius());

System.out.println("Print Area: ");

System.out.println("The area is " + circle.getArea());

System.out.println("Print Circumference: ");

System.out.println("The circumference is " + circle.getCircumference());

System.out.println("Calling toString(): ");

// Calling toString() method

System.out.println(circle);

}

}

========================= Circle.java =========================

public class Circle {

private double radius;

// Default Constructor

public Circle() {

this.radius = 1;

}

// User-specified radius Constructor

public Circle(double radius) {

this.radius = radius;

}

// Method to get Radius

public double getRadius() {

return radius;

}

// Method to set Radius

public void setRadius(double radius) {

this.radius = radius;

}

// Method to calculate Area

public double getArea() {

return 3.14 * radius * radius;

}

// Method to calculate Circumference

public double getCircumference() {

return 2 * 3.14 * radius;

}

// toString method returning Radius, Area and Circumference collectively

@Override

public String toString() {

return "Radius " + " " + radius + ", Area " + getArea() + ", Circumference "+ getCircumference();

}

}

=================== Output =======================

$Console X <terminated> TestCircle [Java Application] C:\Program FilesJavajre1.8.0_65\bin javaw.exe (31-Oct-2018 10:37:52 am) Print radius: The radius is 1.0 Print Area: The area is 3.14 Print Circumference: The circumference is 6.28 Calling toString() Radius 1.0, Area 3.14, Circumference 6.28 Print radius: The radius is 10.0 Print Area: The area is 314.0 Print Circumference: The circumference is 62.800000000000004 Calling toString() Radius 10.0, Area 314.0, Circumference 62.800000000000004$