Inheritance is one of the best concept of Java Programming. Using Object oriented programming it is also a base of defining class.

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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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