Inheritance in Java is a fundamental principal in OOP ( Object-Oriented Programming ) by which one class is allowed to inherit the properties (fields) and behaviors (methods ) of another class .
A class that inherits the another class can reuse the properties of that class .
Example :
//Parent class
class Gift {
void gifName() {
System.out.println(“Gift is awesome”);
}
}
//Child class
class Studentgift extends Gift {
void giftName () {
System.out.println(“Gift is incredible book “);
}
}
//Child class
class Teachergift extends Gift {
void giftName() {
System.out.println(“Gift is $11000”);
}
}
//Main class
public class InheritanceDemo {
public static void main (String args[] ) {
Gift gif ;
gif = new Studentgift();
gif.giftName();
gif = new Teachergift();
gif.giftName();
}
}
OUTPUT:
Gift is incredible book
Gift is $11000
Advantages of Inheritance in Java :
- Reusability of Code : The code written in parent class(super class ) is common to all subclasses . Child classes ( Sub classes ) can directly use the parent class code .
- Method Overriding : Method overriding is achieved by only inheritance . Method overriding is one of the ways by which Java achieves Run Time Polymorphism.
- Abstraction : Abstraction is a process where implementation details are hidden and only shows the functionality to the user . This concept of abstraction is achieved through inheritance .
HOW INHERITANCE WORKS IN JAVA ?
For inheritance concept, extends keyword is used in Java . This extends keyword enables the subclass to inherit the properties of superclass . When a class extends another class , it inherits the properties of the superclass . When a class extends another class , it means it inherits all the non-primitive members of the superclass . The subclass can also override the methods of superclass or can add new functionality to them .
TYPES OF INHERITANCE IN JAVA
Different types of java inheritance are discussed below .
- Single Inheritance :
In Java single inheritance , a sub-class is derived from only one super class . In single inheritance , the sub class inherits the properties & behavior of the parent class .
Example :
//Super class
class Gift {
Gift() {
System.out.println(“Gift is awesome “);
}
}
//Sub class
class StudentGift extends Gift {
StudentGift () {
System.out.println(” Student Gift is an incredible book”);
}
}
public class DemosingleInheritance {
public static void main (String args[] ) {
//Creating object of subclass invokes the superclass constructor
StudentGift sgif= new StudentGift() ;
}
}
OUTPUT:
Gift is awesome
Student Gift is an incredible book
Multilevel Inheritance:
Multilevel inheritance is an java object-oriented programming concept where a class is derived from another class, creating a hierarchial chain of inheritance.
class Gift {
Gift( ) {
System.out.println(“Gift is awesome”);
}
}
class BestgiftWinner extends Gift {
Gift () {
System.out.println(“Best gift winners are incredible”);
}
}
class Studentgift extends BestgiftWinner {
Gift () {
System.out.println(“Students with more than score 90 are winning best gifts”);
}
}
public class DemoMultilevelInheritance {
public static void main (String args[] ) {
Studentgift sgif = new Studentgift ()
}
}
OUTPUT :
Gift is awesome
Best gift winners are incredible
Students with more than score 90 are winning best gifts.
3. Hierarchial Inheritance :
In Java , Hierarchial Inheritance is an object-oriented programming concept where multiple subclasses inherit from a single superclass (parent class ) .
For example : StudentGift and TeacherGift , both are Gift , where Gift is a superclass and StudentGift , TeacherGift are subclass extending the superclass Gift .
Example :
class Gift {
Gift ( ) {
System.out.println(“Gift is awesome”);
}
}
class StudentGift extends Gift {
Gift () {
System.out.println(“Student’s gift is an incredible book”);
}
}
class TeacherGift extends Gift {
Gift ( ) {
System.out.println(“Teacher’s gift is $11000”) ;
}
}
class DemoHierarchialInheritance {
public static void main (String args [ ] ) {
StudentGift sgif = new StudentGift () ;
TeacherGift tgif = new TeacherGift () ;
}
}
OUTPUT :
Gift is awesome
Student’s gift is an incredible book
Gift is awesome
Teacher’s gift is $11000
4. Multiple Inheritance :
Java multiple inheritance is an object-oriented programming concept where a class can inherit from more than one super class (parent class ) . But with java classes multiple inheritance is not possible due to ambiguity problem.
Java class doesn’t support Multiple Inheritance
Java class doesn’t support multiple inheritance due to ambiguity problem.
Example :
import java.io.*;
//First super class
class Gift1 {
void gift () {
System.out.println(“Gift1”);
}
}
//Second Super Class
class Gift2 {
void gift () {
System.out.println(“Gift2”);
}
}
//Inheriting properties of super class1 and super class2
class Demo extends Gift1 , Gift2 {
//main method
public static void main (String args [] ) {
// Creating instance of Demo
Demo d = new Demo () ;
d.gift() ;
}
}
OUTPUT :
Compile time error is thrown
Java Multiple Inheritance can be achieved with Interfaces
Java allows a class to implement multiple interfaces , thus it supports multiple inheritance safely .
interface Gift1 {
default void gift ( ) {
System.out.println ( “Interface Gift1 display”);
}
}
Interface Gift2 {
default void gift ( ) {
System.out.println(“Interface Gift2 display “);
}
}
class Winner implements Gift1 , Gift2 {
@Override
public void gift () {
//Resolving conflict
Gift1.super.gift ( ) ;
Gift2.super.gift () ;
System.out.println (” Class Winner display “) ;
}
}
public class Demo {
public static void main (String args[] ) {
Winner obj = new Winner () ;
obj . gift () ;
}
}
OUTPUT :
Interface Gift1 display
Interface Gift2 display
class Winner display