Java program to illustrate the concept of abstract class

abstract class figure {float l,b;  figure(float x,float y)  {l=x;   b=y; }  abstract float area(); } class rectangle extends figure { rectangle(float a,float b) { super(a,b); } float area() { return(l*b); } } class triangle extends figure {triangle(float a,float b)   {   super(a,b);  }   float area()  {return(l*b/2); } } class figurearea { public static void main(String a[])  {  rectangle r=new rectangle(2.5f,2.5f);   triangle t=new triangle(1f,2.0f);   figure f=r;   System.out.println("area of rectangle="+f.area());   f=t;   System.out.println("area of triangle="+f.area()); } } Output