objected-oriented programming with java
TRANSCRIPT
OBJECT-ORIENTED PROGRAMMING WITH JAVAOum Saokosal, Chief of Computer ScienceNational Polytechnic Institute of CambodiaTel: (855)-12-252-752E-mail: [email protected]
Chapter 6 Objects and Classes(Revision)
• OOP• Classes• Objects• Constructors• Accessing Object’s Data and Methods
Object-Oriented Programming• Why learning OOP?
• Java is a pure OOP• OOP provides more flexibility, modularity, clarity, reusability• Other Programming: C++, C#, VB .NET, ActionScript 3.0, Ruby
etc. also use OOP.
• 3 concepts of OOP:• Class Encapsulation• Class Inheritance• Polymorphism
Classes (1)• What is a class?
• A class is similar to a template, blueprint or symbol (in Adobe Flash).
• A class creates many objects.
Class
Objects
Classes (2)• In a class, there are :
• Data Fields (Properties)• Behavior:
• Constructors• Methods
public class Student {private int id, String name;
public Student(){}
public Student (int inputID, String inputName){this.id = inputID;this.name = inputName;
}public String toString(){
return id + name;}
}
Constructors (1)• What is constructor?
• A constructor is to construct (create) objects from a class.
public class Student {private int id, String name;
public Student(){}
public Student (int inputID,String inputName){this.id = inputID;this.name = inputName;
}public String toString(){
return id + name;}
}
Constructors (2)• How to construct objects?
• Usually, we have many classes in a projects. So the student class will be created in other classes.
• To construct objects from student class:public class TestStudent {public static void main(String[] args){
Student stu;//To construct an objectstu = new Student();System.out.println(stu.toString());
}}
Access Object’s Data and Methods• To access method:public class TestStudent {public static void main(String[] args){
Student stu;//To construct an objectstu = new Student(“123”,”Veasna”);System.out.println(stu.toString());
}}
• To access data:• Usually, We don’t access the data. If you like, you can do like : stu.id = 123 in case id is not private.
END OF REVISION