JAVA SOURCE CODES........

// INHERITANCE BASICS IN JAVA.........
class A

{

int a; void display()

{

System.out.println("A");

}

}
// Use extends keyword for inheritance...........
class B extends A

{

int b;

void display()

{

System.out.println("B");

}

}

class Demo

{

public static void main(String s[])

{

A obj1=new A();

B obj2=new B();

obj1.display();// calls the display function of class A..

// displays "A" on screen..

obj2.display(); // calls the display function of class B

// displays "B" on screen

}

}

// ABSTRACT CLASSES IN JAVA........

abstract class A

{

abstract void display();

}

/* objects of ABSTRACT CLASSES CANT BE CREATED..the functions declared as abstract in base classhas to be defined in the class iheriting the base class*/
class Babstract extends A

{

int a=7;

int b;

void getdata(int C)

{

b=C;

}
void display()

{

System.out.println("a is:"+a);

System.out.println("b is:"+b);

}

}

class demo

{

public static void main(String s[])

{

Babstract obj1=new Babstract();

obj1.getdata(20);

obj1.display(); /* displays a is: 7 b is: 20 */

}

}

/* TYPES OF CONTRUCTORS........

1: default constuctor...without any parameters..

2: parametrised constructor...with constructors..

3: copy constructor..that takes objects of its class as parameters... */

public class constr

{

int a=51;

int b=7;
// default... constr()

{

System.out.println("hello");

}

// parametrised......

constr(int a,int b)

{

this.a=a;

this.b=b;

}

// copy .......

constr(constr ob)

{

this.a=ob.a;

this.b=ob.b;

}

void display()

{

System.out.println("a is:"+a);

System.out.println("b is:"+b);

}

public static void main(String s[])

{

constr obj1=new constr();// prints hello

obj1.display(); //displays default values i.e 51,7
constr obj2=new constr(5,6);//initialises a,b by 5,6 resp.

obj2.display(); // displays 5 and 6

constr obj3=new constr(obj2);//copies values of obj2 to obj3

obj3.display() // displays 5,6

}

}