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Introduction to Object Oriented Programming
- 1. Introduction to Object Oriented Programming MD. Tanvir Hossain Student, Dept of CSE Daffodil International University 1
- 2. Object-Oriented Language In structured programming languages, methods define the structure of the programs, they are basic building blocks Data has secondary role, it is just something that is passed around. In object oriented languages, the data has the principal role Methods belong to the data, without the data, the method does not have any meaning (Except static methods) Data and methods together make up the object. OOP tries to model the real world. What does the real world look like? 2
- 3. Objects everywhere... Real world entities 3
- 5. Objects have behavior…. Hello, I am John Nice to meet you da da … Grrrrrrrr Vroemm 5
- 6. World The world is • a set of things • interacting with each other. OOP is more natural to humans, but less natural to computers Computers (usually) have a single thread of control, so objects take turns 6
- 7. Describing the world Describe a particular person • Ayman has long blond hair, green eyes, is 1.63m tall, weighs 56Kg and studies computer engineering. Now lying down asleep. • Mahmud studies electronics, has short black hair and brown eyes. He is 180cm and 75 kilos. Now running to class! Notice how all have specific values of • name, height, weight, eye colour, state, … 7
- 8. Advantages of OOP Simplicity: software objects model real world objects, so the complexity is reduced and the program structure is very clear; Modularity: each object forms a separate entity whose internal workings are decoupled from other parts of the system; Modifiability: it is easy to make minor changes in the data representation or the procedures in an OO program. Changes inside a class do not affect any other part of a program, since the only public interface that the external world has to a class is through the use of methods. 8
- 9. Extensibility: adding new features or responding to changing operating environments can be solved by introducing a few new objects and modifying some existing ones. Maintainability: objects can be maintained separately, making locating and fixing problems easier. Re-usability: objects can be reused in different programs. 9 Advantages of OOP
- 10. Features of OOP 10 Classes Data Abstraction Encapsulation Inheritance Polymorphism Information Hiding
- 11. Class and Object 11 CLASS: Basic building blocks of OOP. Once a class has been defined, we can create any number of objects belonging to that class. OBJECT: Objects are instances or variables of the type class. Objects has real existence and take up space in the memory. When a program is executed , the objects interact by sending messages to one another. Each object contain data and code to manipulate the data.
- 12. Object Properties Identity State Behavior myLamp on off Object is an abstraction of a real world entity 12
- 13. Introduction to Objects An object represents something with which we can interact in a program An object provides a collection of services that we can tell it to perform for us The services are defined by methods in a class that defines the object A class represents a concept, and an object represents the embodiment of a class A class can be used to create multiple objects 13
- 14. Objects and Classes Bank Account A class (the concept) John’s Bank Account Balance: $5,257 An object (the realization) Bill’s Bank Account Balance: $1,245,069 Mary’s Bank Account Balance: $16,833 Multiple objects from the same class 14
- 15. 15 Abstraction Hiding the complexity of program is called Abstraction and only essential features are represented. In short we can say that internal working is hidden. Abstraction A car consists of four wheels an engine, accumulator and brakes.
- 16. Encapsulation Combining data and functions into a single unit called class and the process is known as Encapsulation. Data encapsulation is important feature of a class. Class contains both data and functions. Data is not accessible from the outside world and only those function which are present in the class can access the data. 16
- 17. Refers to linking of function call with function definition is called binding and when it is take place at run time called dynamic binding. 17 Dynamic Binding
- 18. Message Passing The process by which one object interact with other object is called message passing. 18
- 19. Inheritance It is the process by which object of one class acquire the properties or features of objects of another class. The concept of inheritance provide the idea of reusability means we can add additional features to an existing class without Modifying it. This is possible by driving a new class from the existing one. The new class will have the combined features of both the classes. 19
- 21. Polymorphism The term polymorphism literally means "having many forms" A polymorphic reference is a variable that can refer to different types of objects at different points in time The method invoked through a polymorphic reference can change from one invocation to the next All object references in Java are potentially polymorphic 21
- 23. Polymorphism 23