Question

How to use this to invoke a constructor in Java

Answer 1

public class Circle {
    double radius;
    public Circle() {
        this(10);
        System.out.println("public Circle()");
    }
    Circle(double radius) {
        System.out.println("Circle(double radius)");
        this.radius = radius;
    }
    double Area() {
        return Math.PI * this.radius * this.radius ;    
    }
    double Perimeter() {
        return 2 * Math.PI * this.radius;
    }
    void set_radius(double radius) {
        this.radius = radius;
    }
    public static void main(String args[]) {
        Circle circle1 = new Circle();
        System.out.println(circle1.Area());
        System.out.println(circle1.Perimeter());
    }
}
 
 
/*
run:
 
Circle(double radius)
314.1592653589793
62.83185307179586
 
*/

 

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