abstract class in java

abstract class Figure { double dim1; double dim2; Figure(double a,double b) { dim1=a; dim2=b; } abstract double area(); } class Rectangle extends Figure { Rectangle(double a,double b) { super(a,b); } double area() { System.out.println("Area of Rectangle:"); return dim1*dim2; } } class Triangle extends Figure { Triangle(double a,double b) { super(a,b); } double area() { System.out.println("Area of Triangle"); return((dim1*dim2)/2); } } class Abs { public static void main(String args[]) { Figure f=new Figure(10,10); Rectangle r=new Rectangle(10,12); Triangle t=new Triangle(10,18); Figure fig; fig=f; System.out.println(fig.area()); fig=r; System.out.println(fig.area()); fig=t; System.out.println(fig.area()); } }