What is an Inheritance?

  What is an Inheritance?

The derivation of one class from another class is called Inheritance.

A class that is inherited is called a super class.

The class that does the inheriting is called as subclass.

A subclass inherits all instance variables and methods from its super class and also has its own variables and methods.

One can inherit the class using keyword extends.

In java, a class has only one super class.

Java does not support Multiple Inheritance.

One can create a hierarchy of inheritance in which a subclass becomes a super class of another subclass.

However, no class can be a super class of itself. 

 Why use Inheritance?

For Method Overriding (So Runtime Polymorphism). 

For Code Reusability

Syntax:-

Class subclass-name extends super class-name

{

        // body of class.

}

 Example of inheritance 

Programmer is the subclass and Employee is the super class. Relationship between two classes is Programmer IS-A Employee. It means that Programmer is a type of Employee.

         class Employee

{
          int salary=40000; //member of super class

}

class Programmer extends Employee

{

         

int  bonus=10000; //member of subclass

Public Static void main(String args[])

{

Programmer p=new Programmers;
System.out.println(”Programmer salary is: “+ p.salary);
System.out.println(“Bonus of Programmer is: “+ p.bonus);

                   }

          }

Ø  Output:

Programmer salary is: 40000
Bonus of Programmer is:10000

Note: Private members of super class is not accessible in subclass, super class is also called parent class or base class, Subclass is also called child class or derived class.

v  Types of Inheritance:-

      

1) Single

2) Multilevel

3) Hierarchical 

ð  Note: Multiple inheritance is not supported in java in case of class.

ð  When a class extends two classes known as multiple inheritance.

Why multiple inheritance is not supported in java?

ð  To reduce the complexity and simplify the language, multiple inheritance is not supported in java.

ð  For Example:

class Tester

{

void msg()

{

                    System.out.println(”Hello”);     

}

}

class Programmer

{

          void msg()

          {

                   System.out.println(“Welcome”);

          }

}
class Company extends Tester, Programmer

{

          public static void main(String args[])

          {                

                    Company obj=new Company();

                    obj.msg;    //Now which msg() method would be invoked?

          }

}