Question:

Consider the following Java code snippet:

public class Circle {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    public double getRadius() {
        return radius;
    }

    public void setRadius(double radius) {
        this.radius = radius;
    }

    public double getArea() {
        return Math.PI * radius * radius;
    }

    public double getCircumference() {
        return 2 * Math.PI * radius;
    }
}

Explain what instance variables and methods are present in the Circle class. Additionally, provide a step-by-step explanation of how to calculate the area and circumference of a circle using the Circle class.

Answer:

The Circle class has the following instance variable and methods:

Instance Variable:

• radius: A private double variable that represents the radius of the circle.

Methods:

1. Circle(double radius): A constructor that initializes the radius instance variable with the value passed as a parameter.
2. getRadius(): A getter method that returns the value of the radius instance variable.
3. setRadius(double radius): A setter method that sets the value of the radius instance variable.
4. getArea(): A method that calculates and returns the area of the circle using the formula Math.PI * radius * radius.
5. getCircumference(): A method that calculates and returns the circumference of the circle using the formula 2 * Math.PI * radius.

To calculate the area and circumference of a circle using the Circle class, follow these steps:

1. Create an instance of the Circle class by calling the constructor and passing the desired radius as a parameter. For example, to create a circle with a radius of 5.0:

Circle circle = new Circle(5.0);

2. To get the radius of the circle, call the getRadius() method on the circle object and store the returned value in a variable.

double radius = circle.getRadius();

3. To calculate the area of the circle, call the getArea() method on the circle object and store the returned value in a variable.

double area = circle.getArea();

4. To calculate the circumference of the circle, call the getCircumference() method on the circle object and store the returned value in a variable.

double circumference = circle.getCircumference();

5. You can now use the values of area and circumference for further calculations or display them as desired.