public class L1106 {    public static void main(String[] args) {        // TODO Auto-generated method stub        TestDemo circle1 = new TestDemo();        double area=circle1.getArea();        System.out.println(area);        TestDemo circle2=new TestDemo(10);        System.out.println(circle2.getArea());        System.out.println(circle1.getPerimeter());        System.out.println(circle2.getPerimeter());        double ridius=10;        double areaCircle=Math.PI*ridius*ridius;        System.out.println(areaCircle);        circle2.setRadius(5);        System.out.println(circle2.getArea());    }}

public class TestDemo {private double radius;        public TestDemo(double radius) {        this.radius = radius;    }    public TestDemo() {        this.radius = 1.0;    }    public double getArea() {        return Math.PI * radius * radius;    }    public double getPerimeter() {        return 2 * Math.PI * radius;    }    public void setRadius(double newRadius) {        this.radius = newRadius;    }}