using System;

class MainClass {

public static void Main (string[] args) {

​

    // Declare an instance of Circle class called c1.

    // Construct the instance c1 by invoking the "default" constructor

    // which sets its radius and colour to their default value.

    Circle c1 = new Circle();

    // Invoke public methods on instance c1, via dot operator.

        Console.WriteLine("The circle has radius of "+ c1.getRadius() + " and area of "+ c1.getArea());

    //The circle has radius of 1.0 and area of 3.141592653589793

    // Declare an instance of class circle called c2.

    // Construct the instance c2 by invoking the second constructor // with the given radius and default colour.

    Circle c2 = new Circle (2.0);

    // Invoke public methods on instance c2, via dot operator. 

        Console.WriteLine("The circle has radius of "+ c2.getRadius() + " and area of " + c2.getArea());

    //The circle has radius of 2.0 and area of 12.566370614359172

    Circle c3 = new Circle (3.0, "red");

        Console.WriteLine("The circle has radius of "+ c3.getRadius() + " and area of " + c3.getArea() + "and the colour is " + c3.getColour());

    Circle c4 = new Circle(); // construct an instance of Circle 

        c4.setRadius(5.5);// change radius

        Console.WriteLine("Radius is: " + c4.getRadius()); // Print radius via getter 

        c4.setColour("green");  // Change colour

        Console.WriteLine("Colour is: " + c4.getColour() ); // Print colour via getter

    // You cannot do the following because setRadius() returns void, which cannot be printed //Console.WriteLine(c4.setRadius (4.4));

    Circle c5 = new Circle(5.5); 

        Console.WriteLine(c5.toString()); // explicit call

    }

}

​

​

​

​

// The Circle class models a circle with a radius and colour.

class Circle {

// private instance variable, not accessible from outside this class

    private double radius;

    private string colour;

//Constructs a Circle instance with default value for radius and colour

    public Circle() { // 1st (default) constructor

    this.radius = 1.0;

    this.colour="red";

    }

    //Constructs a Circle instance with the given radius and default colour */ 

    public Circle(double r) { // 2nd constructor

    this.radius = r;

    this.colour = "red";

    }

    // Returns the radius

    public double getRadius() {

    return radius;

    }

    // Returns the area of this Circle instance 

    public double getArea() {

    return radius*radius*Math.PI;

    }

    // 3rd constructor to construct a new instance of Circle with the given radius and colour

    public Circle (double r, string c) {

        this.radius = 3.0;

        this.colour="red";

    }

    // Getter for instance variable colour 

    public string getColour() {

        return colour;

    }

    // Setter for instance variable radius

    public void setRadius (double newRadius) { 

        this.radius = newRadius;

    }

    // Setter for instance variable colour 

    public void setColour (String newColour) {

        this.colour = newColour;

    }

    public string toString() { 

        return "Circle[radius=" + radius + " colour=" + colour + "]"; 

    }

}