Pr2b.java

abstract class Shape {

  public abstract double area();
}

class Circle extends Shape {

  private double radius;

  public Circle(double radius) {
    this.radius = radius;
  }

  @Override
  public double area() {
    return Math.PI * radius * radius;
  }
}

public class Pr2b {

  public static void main(String args[]) {
    Circle c = new Circle(10.0);
    System.out.println("Area of Circle=" + c.area());
  }
}