Java Inheritance and Polymorphism

Java Inheritance and Polymorphism

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  Java Inheritance &Polymorphism Kadarkarai Selvam
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  Inheritance ❖ Inheriting thestate and behaviours from a class ❖ It is parent child relationship where child can have all the fields and methods. ❖ Child can have new fields and methods other than the methods inherited from Parents
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  Class Vehicle{ int noofwheels; Stringname, manufacturer; acceleration(){ //method statements } } Class ElectricCars extends Vehicle{ float batterycapacity; charging(){ //statements can use fields from Vehicle & ElectricCar } } Child class Super class Inheritance Type - Single
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  Multiple and MultilevelInheritance
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  Hierarchical and HybridInheritance
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  Polymorphism ❖ An Objector Entity can do action in different ways ❖ With different situation same object possess different qualities. ❖ E.g., A man can be a father, husband, son, employee etc. ❖ In Java, Polymorphism is achieved by two ways ➢ Compile time Polymorphism ➢ Run time Polymorphism
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  Compile Time Polymorphism ❖Also known as Static Polymorphism ❖ Achieved by Method Overloading in Java ❖ Here call to method is resolved at run time. ❖ Methods have same name but with any of the following difference makes the method to overload ➢ Different parameters ➢ Different types of parameters ➢ Change in order of parameters ➢ Different return type
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  public class MethodOverloading{ void sum(int a, int b) { int c = a+b; System.out.println("sum of value "+c); } void sum(int a, double b) { double c = a+b; System.out.println("sum of value "+c); } void sum(double a, int b) { double c = a+b; System.out.println("sum of value "+c); } int sum(int a, int b, int c) { int d = a+b+c; System.out.println("sum of value "+c); return d; } }
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  Run time Polymorphism ❖Overloaded method is called by a reference variable of Parent / Super class ❖ In Real world example, 3 programmers are working on a module Bikes ➢ One in Bikes base class ➢ Other working in BWM class which is extended from Bikes class ➢ Other working in Unicorn class which is extended from Bikes class ❖ Each Class have the method acceleration and each bikes have different acceleration ❖ So one can create object for a child class(unicorn/BMW) with reference from Parent class(Bikes) Check this for detailed explanation
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  What is AccessModifiers ❖ Describes the Scope (or) Accessibility of a state or behaviour or class itself ❖ This will create the visibility of the fields, constructor or methods or class to other entities. ❖ Four Majorly used Access modifiers are ➢ Private ➢ Default ➢ Public ➢ Protected
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  Access Modifier WithinClass Within Package Outside Package Private Y N N Default Y Y N Protected Y Y N Public Y Y Y
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