Lect 2.5 Polymorphism in various languages

Lect 2.5 Polymorphism in various languages - Lecture2.5...

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Lecture 2.5 Polymorphism in C++, Java and C#
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What is polymorphism Polymorphism is the ability of a particular type (or class) B to appear like its base type A. If B is a subclass of A, then we can have oA = oB where oA and oB are variables of types A and B respectively. Polymorphism is supported in C++, Java and C#. In particular, C# share common polymorphic features with Java and C++. 2
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Polymorphism Polymorphism is useful because sometimes we do not know the exact type of an object during compile time Hence we use the base class variable to refer to it and we want the behavior of the object to be correct (of its class) and not incorrectly reflect the behavior of the base class 3
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Examples of polymorphism Here we consider two examples Base class Animal Abstract class (because there is no specific living organism called Animal). Subclasses can include Lion, Horse, Elephant etc. Base class Employee Non abstract class Subclasses can include Manager, Intern etc. An abstract class, in computer science terminology, is a class where instantiation of objects is not allowed. 4
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Abstract base class Animal (generic) class Animal { float averagelifespan; float getAveragelifespan() { return averagelifespan; } void makeSound(); // no body } class Lion (inherits from Animal) { Lion() { averagelifespan = 20; } void makeSound() { // plays Roar.wav } } 5 ….. Animal[] list = new Animal[10]; Here each animal in the list should make the appropriate sound according to its species. for (int i=0; i<10; i++) { list[i].makeSound(); } should play the correct .wav file for each animal (be it Lion, Horse, Elephant)
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About the abstract base class Animal It has an attribute averagelifespan that is applicable for all subclasses.
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