12

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;
     }
 }