package javaDemo; public class TestDemo { public static void main(String []args){ System.out.println("Square's area:\t"+(new Square()).area(2)); System.out.println("Circle's area:\t"+(new Circle()).area(3)); } } interface Shape{ abstract double area(double one); } class Square implements Shape{ public double area(double one){ return one*one; } } class Circle implements Shape{ public double area(double two){ return Math.PI*Math.pow(two,2); } }