Lect 2.5 Polymorphism in various languages

Lect 2.5 Polymorphism in various languages - Lecture2.5

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 2.5 Polymorphism in C++, Java and C#
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
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
Background image of page 2
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
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
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
Background image of page 4
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)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
About the abstract base class Animal It has an attribute averagelifespan that is applicable for all subclasses. It also has an accessor method
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/08/2010 for the course SCE CSC301 taught by Professor Mr.leong during the Fall '10 term at Nanyang Technological University.

Page1 / 17

Lect 2.5 Polymorphism in various languages - Lecture2.5

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online