Question

How to define a class and create objects that calculate area and perimeter of a circle in Java

Answer 1

public class Circle {
    double radius;
    Circle() {
        radius = 10;
    }
    Circle(double new_radius) {
        radius = new_radius;
    }
    double Area() {
        return Math.PI * radius * radius ;    
    }
    double Perimeter() {
        return 2 * Math.PI * radius;
    }
    void set_radius(double new_radius) {
        radius = new_radius;
    }
    public static void main(String args[]) {
        Circle circle1 = new Circle();
        System.out.println(circle1.Area());
        System.out.println(circle1.Perimeter() + "\n");
        
        Circle circle2 = new Circle(30);
        System.out.println(circle2.Area());
        System.out.println(circle2.Perimeter() + "\n");
        
        circle1.set_radius(15);
        System.out.println(circle1.Area());
        System.out.println(circle1.Perimeter());
    }
}


/*
run:

314.1592653589793
62.83185307179586

2827.4333882308138
188.49555921538757

706.8583470577034
94.24777960769379

*/

 

70+ SQL courses for beginners and professionals