INHERITANCE IN OOPS

Sharda University

Department Of Computer Science And Engineering

School Of Engineering And Technology

Greater Noida, U. P.

Presented By Hirra Sultan

CSE-B 2nd yearRoll No. 120101091

Enrollment No. 2012017740Supervisor: Mr. A. K. Sahoo

prlhirr@gmail.com

Introduction

Background The first OOP language designed for the

first personal computer was smalltalk. When OOP was integrated into C

language, the resulting language was called C++ and it became the first object-oriented language to be widely used commercially.

Later java and other OOP languages were developed.

Concept of Inheritance Inheritance is that feature of an OOP language

which allows reusability of code of a class and is considered corner stone of OOP languages.

Using inheritance, we can create a general class that defines traits common to a set of related items.

This class may then be inherited by other, more specific classes, each adding only those things that are unique to the inheriting class.

Base class: The class which gets inherited is called a base class. The code of this class is passed on to subclasses where it is reused.

Derived class: A subclass is a derived class which inherits the base class and uses its member functions.

Un-inheritable class: A class may be declared as un-inheritable by adding certain class modifiers to the class declaration before the "class" keyword and the class identifier declaration. Such sealed classes restrict reusability.

Definitions

Types of Inheritance

Single Inheritance: In single inheritance there is only one super class and only one sub class.

Multi-level inheritance: In multi-level inheritance a derived class is inherited by another class thus making multiple levels.

Multiple Inheritance: A class can inherit the attributes of two or more classes. This is known as multiple inheritance.

Hierarchical inheritance: When a base class is inherited by multiple derived classes it is called hierarchical inheritance.

Hybrid inheritance: This is a mixture of two or more inheritances in a single code.

Inheritance may be derived in three forms which decides the way inherited data members can be used. Public Inheritance: Public members of

the base class become public members of the derived class and protected members of the base class become protected members of the derived class.

Protected Inheritance: When deriving from a protected base class, public and protected members of the base class become protected members of the derived class.

Private Inheritance: When deriving from a private base class, public and protected members of the base class become private members of the derived class.

Inheritance in C++ In C++ all the five types of inheritances are

applicable. Friend functions and constructors can’t be

inherited. The general syntax of inheritance is:

class derived-class-name : visibility-mode base-class-name

{

…// members of derived class

};

Inheritance in Java The general syntax of inheritance is:

Class Subclass-name extends superclass-name

{

//methods and fields

}

The keyword extends indicates that we are making a new class that derives from an existing class.

Multiple and hybrid inheritance is not supported. This reduces the program complexity.

Constructors are not inherited by a subclass.

Inheritance in Python Instances inherit from classes, and classes

inherit from super classes. Python supports a limited form of multiple

inheritance. The syntax for inheritance in python is:

class DerivedClassname (BaseClassName):

<statement-1>

.

<statement-N>

Inheritance in ADA

In Ada 95 terminology, types that can have parents or children are termed “tagged types”, and have the keyword “tagged” as part of their definition.

If we don't redefine a subprogram for a given type, the closest ancestor's defined subprogram will be used.

Advantages

We save time because much of the code needed for our class is already written.

We can extend and revise a parent class without corrupting the existing parent class features.

Disadvantages

Removing or swapping out a superclass will usually break subclasses.

It's inflexible. Inheritance relationships generally can't

be altered at runtime.