program to demonstrate concept of Inheritance, Abstract class and abstract method.

/*
Aim : Write a program to demonstrate concept of Inheritance, Abstract class and abstract method.
*/
import java.lang.*;

abstract class figure    //abstract class
{
double d1;
double d2;

figure(double a,double b) //constructor
{
d1=a;
d2=b;
}

abstract double area(); //abstract method
}

class trangle extends figure
{
trangle(double a,double b) //constructor of derived class
{
super(a,b); //call to base class constructor
}

double area()
{
System.out.println("\tInside the area of Trangle....");
return(0.5*d1*d2);
}
}

class rectangle extends figure
{
rectangle(double a,double b) //constructor of derived class
{
super(a,b); //call to base class constructor
}

double area()
{
System.out.println("\tInside the area of Trangle....");
return(d1*d2);
}
}

class circle extends figure
{
circle(double a,double b) //constructor of derived class
{
super(a,b); //call to base class constructor
}

double area()
{
System.out.println("\tInside the area of circle....");
return(2*d1*d2*d2);
}
}

class pr_2
{
public static void main(String argv[])
{
figure ref;
rectangle rect = new rectangle(10,20);
trangle t = new trangle(34,12);
circle cir = new circle(3.14,5);

ref=rect;
System.out.println("\tArea is : "+ref.area());
ref=t;
System.out.println("\tArea is : "+ref.area());
ref=cir;
System.out.println("\tArea is : "+ref.area());
}
}

/* OUTPUT
prashant@prashant-OptiPlex-755:~$ javac pr_2.java
prashant@prashant-OptiPlex-755:~$ java pr_2
Inside the area of Trangle....
Area is : 200.0
Inside the area of Trangle....
Area is : 204.0
Inside the area of circle....
Area is : 157.0
prashant@prashant-OptiPlex-755:~$
*/