The extends Keyword in Java

An object can acquire the properties and behaviour of another object using Inheritance. In Java, the extends keyword is used to indicate that a new class is derived from the base class using inheritance. So basically, extends keyword is used to extend the functionality of the class.

A program that demonstrates the extends keyword in Java is given as follows:

Example

 Live Demo

class A {    int a = 9; } class B extends A {    int b = 4; } public class Demo {    public static void main(String args[]) {       B obj = new B();       System.out.println("Value of a is: " + obj.a);       System.out.println("Value of b is: " + obj.b);    } }

Output

Value of a is: 9 Value of b is: 4

Now let us understand the above program.

The class A contains a data member a. The class B uses the extends keyword to derive from class A. It also contains a data member b. A code snippet which demonstrates this is as follows:

class A {    int a = 9; } class B extends A {    int b = 4; }

In the main() method in class Demo, an object obj of class B is created. Then the values of a and b are printed. A code snippet which demonstrates this is as follows:

public class Demo {    public static void main(String args[]) {       B obj = new B();       System.out.println("Value of a is: " + obj.a);       System.out.println("Value of b is: " + obj.b);    } }