Bài giảng lập trình c 2010 chương 5 đh công nghệ đồng nai

DONG NAI UNIVERSITY OF TECHNOLOGY DONG NAI UNIVERSITY OF TECHNOLOGY DONG NAI UNIVERSITY OF TECHNOLOGY Abstraction Encapsulation Inheritance Polymorphism DONG NAI UNIVERSITY OF TECHNOLOGY Abstraction Characteristics Properties Object Behaviors  Methods DONG NAI UNIVERSITY OF TECHNOLOGY Encapsulation Characteristics Behaviors Properties  Methods Package DONG NAI UNIVERSITY OF TECHNOLOGY Encapsulation private protected public DONG NAI UNIVERSITY OF TECHNOLOGY Inheritance • The ability to create a new class from an existing class • The existing class is called the base, superclass, or parent • The inherited class is called the derived, subclass, or child • A derived class has an “is a” relationship with its base class DONG NAI UNIVERSITY OF TECHNOLOGY Inheritance DONG NAI UNIVERSITY OF TECHNOLOGY Inheritance • • Inheritance supports reusability Reusability – creation of object functionality that may be used in multiple projects DONG NAI UNIVERSITY OF TECHNOLOGY Polymorphism • • Methods with identical names have different implementations The Select method is different for radio buttons, check boxes, and list boxes • Allows a single class to have more than one method with different argument lists DONG NAI UNIVERSITY OF TECHNOLOGY How to create Class DONG NAI UNIVERSITY OF TECHNOLOGY Class Name Constructors Attributes Properties Methods DONG NAI UNIVERSITY OF TECHNOLOGY public abstract class CAbstractProduct { private string m_strID; private string m_strName; Attributes private string m_strDescription; public CAbstractProduct() { } Constructor public string ID { get { return this.m_strID; } set { this.m_strID = value; } } public string Name { Properties get { return this.m_strName; } set { this.m_strName = value; } } public string Description { get { return this.m_strDescription; } set { this.m_strDescription = value; } } public abstract void doSomething(); } Methods DONG NAI UNIVERSITY OF TECHNOLOGY public class CProduct : CAbstractProduct { private double m_dPrice; public CProduct() { } public double Price { get { return this.m_dPrice; } set { this.m_dPrice = value; } } public override void doSomething() { throw new NotImplementedException(); } } public class CBook:CProduct { private string m_strISBN; private string m_strAuthor; private string m_strTitle; public CBook() { } public string ISBN { get { return this.m_strISBN; } set { this.m_strISBN = value; } } public string Author { get { return this.m_strAuthor; } set { this.m_strAuthor = value; } } public string Title { get { return this.m_strTitle; } set { this.m_strTitle = value; } } } DONG NAI UNIVERSITY OF TECHNOLOGY DONG NAI UNIVERSITY OF TECHNOLOGY public class CCompactDisc:CProduct { private string m_strArtist; private string m_strTitle; public CCompactDisc() { } public string Artist { get { return this.m_strArtist; } set { this.m_strArtist = value; } } public string Title { get { return this.m_strTitle; } set { this.m_strTitle = value; } } public override void doSomething() { throw new NotImplementedException(); } } DONG NAI UNIVERSITY OF TECHNOLOGY public class CTravelGuide:CBook { private string m_strCountry; public CTravelGuide() { } public string Country { get { return this.m_strCountry; } set { this.m_strCountry = value; } } } DONG NAI UNIVERSITY OF TECHNOLOGY Garbage Collection DONG NAI UNIVERSITY OF TECHNOLOGY • • • Operator new allocates memory When objects are no longer referenced, the CLR performs garbage collection Garbage collection helps avoid memory leaks (running out of memory because unused memory has not been reclaimed) • Allocation and deallocation of other resources (database connections, file access, etc.) must be explicitly handled by programmers DONG NAI UNIVERSITY OF TECHNOLOGY • Use finalizers in conjunction with the garbage collector to release resources and memory • Before garbage collector reclaims an object’s memory, it calls the object’s finalizer • • • Each class has only one finalizer (also called destructor) Name of a destructor is the ~ character, followed by the class name Destructors not receive any arguments DONG NAI UNIVERSITY OF TECHNOLOGY public class CTravelGuide:CBook { private string m_strCountry; public CTravelGuide() { } public string Country { get { return this.m_strCountry; } set { this.m_strCountry = value; } } ~CTravelGuide() { Console.WriteLine("deconstructor"); } } DONG NAI UNIVERSITY OF TECHNOLOGY END [...]... garbage collector to release resources and memory • Before garbage collector reclaims an object’s memory, it calls the object’s finalizer • • • Each class has only one finalizer (also called destructor) Name of a destructor is the ~ character, followed by the class name Destructors do not receive any arguments DONG NAI UNIVERSITY OF TECHNOLOGY public class CTravelGuide:CBook { private string m_strCountry;...DONG NAI UNIVERSITY OF TECHNOLOGY How to create Class DONG NAI UNIVERSITY OF TECHNOLOGY Class Name Constructors Attributes Properties Methods DONG NAI UNIVERSITY OF TECHNOLOGY public abstract class CAbstractProduct { private string m_strID; private string m_strName; Attributes private string m_strDescription; public CAbstractProduct() { } Constructor public string ID { get { return... allocates memory When objects are no longer referenced, the CLR performs garbage collection Garbage collection helps avoid memory leaks (running out of memory because unused memory has not been reclaimed) • Allocation and deallocation of other resources (database connections, file access, etc.) must be explicitly handled by programmers DONG NAI UNIVERSITY OF TECHNOLOGY • Use finalizers in conjunction... } public string Name { Properties get { return this.m_strName; } set { this.m_strName = value; } } public string Description { get { return this.m_strDescription; } set { this.m_strDescription = value; } } public abstract void doSomething(); } Methods DONG NAI UNIVERSITY OF TECHNOLOGY public class CProduct : CAbstractProduct { private double m_dPrice; public CProduct() { } public double Price { get... value; } } public override void doSomething() { throw new NotImplementedException(); } } DONG NAI UNIVERSITY OF TECHNOLOGY public class CTravelGuide:CBook { private string m_strCountry; public CTravelGuide() { } public string Country { get { return this.m_strCountry; } set { this.m_strCountry = value; } } } DONG NAI UNIVERSITY OF TECHNOLOGY Garbage Collection DONG NAI UNIVERSITY OF TECHNOLOGY • • •... value; } } public string Title { get { return this.m_strTitle; } set { this.m_strTitle = value; } } } DONG NAI UNIVERSITY OF TECHNOLOGY DONG NAI UNIVERSITY OF TECHNOLOGY public class CCompactDisc:CProduct { private string m_strArtist; private string m_strTitle; public CCompactDisc() { } public string Artist { get { return this.m_strArtist; } set { this.m_strArtist = value; } } public string Title {... Price { get { return this.m_dPrice; } set { this.m_dPrice = value; } } public override void doSomething() { throw new NotImplementedException(); } } public class CBook:CProduct { private string m_strISBN; private string m_strAuthor; private string m_strTitle; public CBook() { } public string ISBN { get { return this.m_strISBN; } set { this.m_strISBN = value; } } public string Author { get { return this.m_strAuthor;... DONG NAI UNIVERSITY OF TECHNOLOGY public class CTravelGuide:CBook { private string m_strCountry; public CTravelGuide() { } public string Country { get { return this.m_strCountry; } set { this.m_strCountry = value; } } ~CTravelGuide() { Console.WriteLine("deconstructor"); } } DONG NAI UNIVERSITY OF TECHNOLOGY END ... public abstract void doSomething(); } Methods DONG NAI UNIVERSITY OF TECHNOLOGY public class CProduct : CAbstractProduct { private double m_dPrice; public CProduct() { } public double Price {... DONG NAI UNIVERSITY OF TECHNOLOGY How to create Class DONG NAI UNIVERSITY OF TECHNOLOGY Class Name Constructors Attributes Properties Methods DONG NAI UNIVERSITY OF TECHNOLOGY public abstract class... (also called destructor) Name of a destructor is the ~ character, followed by the class name Destructors not receive any arguments DONG NAI UNIVERSITY OF TECHNOLOGY public class CTravelGuide:CBook