The document discusses the concept of inheritance in object-oriented programming (OOP), highlighting its importance in reusability and defining relationships between classes. It explains the is-a relationship and types of inheritance in Java, including single, multilevel, and hierarchical inheritance, while also addressing why multiple inheritance is not supported. The document emphasizes that inheritance allows subclasses to inherit attributes and methods from their superclasses, enabling better code management.

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Inheritance

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OOP
Encapsulation
Inheritance
Polymorphism
Abstraction
4 pillars of OOPS

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Inheritance
 Inheritance is a fundamental Object Oriented concept
 A class can be defined as a "subclass" of another class.
 The subclass inherits all data attributes of its superclass
 The subclass inherits all methods of its superclass
 The subclass inherits all associations of its superclass

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Inheritance(Continue…)
 When we talk about inheritance, the most commonly used keyword would be extends and
implements.
Class
Class
extends
Interface
Class
implements
Interface
Interface
extends

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Inheritance(Continue…)
 These words would determine whether one object IS-A type of another.
IS-A Relationship:
 IS-A is a way of saying : This object is a type of that object.
Surgeon IS-A Doctor

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Inheritance(Continue…)
 Now, if we consider the IS-A relationship:
1. Mammal IS-AAnimal
2. Reptile IS-AAnimal
3. Dog IS-A Mammal
Hence : Dog IS-AAnimal as well

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Inheritance(Continue…)
 Reusability is achieved by INHERITANCE
 Java classes Can be Reused by extending a class. Extending an existing class is nothing but
reusing properties of the existing classes.
 The class whose properties are extended is known as super or base or parent class.
 The class which extends the properties of super class is known as sub or derived or child
class
 A class can either extends another class or can implement an interface

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Example

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Why use inheritance in java
 For Method Overriding (so runtime polymorphism can be achieved).
 For Code Reusability.

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Types of inheritance in java
 On the basis of class, there can be three types of inheritance in java:
 Single, multilevel and hierarchical.
 In java programming, multiple and hybrid inheritance is supported through interface only.

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Various Forms of Inheritance
A
B
Single Inheritance Hierarchical Inheritance
X
A B C
Multilevel Inheritance
A
B
C
A B
C
Multiple Inheritance
NOT SUPPORTED BY JAVA A B
C
A C
Hybrid Inheritance

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Why multiple inheritance is not
supported in java?
 To reduce the complexity and simplify the language, multiple inheritance is not supported in
java.
 Consider a scenario where A, B and C are three classes.
 The C class inherits A and B classes.
 If A and B classes have same method and you call it from child class object, there will be
ambiguity to call method of A or B class.

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