1. CSC238
INTRODUCTION TO OOP
Chapter 1

2. Objectives At the end of this topic, you should be able to
know the elements of an object.
differentiate between objects and classes.
understand the characteristics of OOP.
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3. Object Objects are key to understanding object-oriented technology.
In real life, things that you see such as cars, trees, cats, mobile phones and so on are objects. Even, you as a student is an object.
Each object has states , behaviours and identity.
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4. Elements of an Object OBJECT
Attribute /state – properties used to define characteristics.
OBJECT
Behaviour – means the object can perform actions & can have actions performed on it.
Identity – means the object can be called & used as a single unit.
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5. Example 1:
An air-conditioner at MK02
State : Turn on Current temperature is at 20 degree celcius Behaviours : Change the temperature level
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6. Example 2:
A Siamese Cat
State : Dark brown colours on its face, ears and feet Behaviours : Playing, fighting, hunting
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7. Example 3:
How about the following cats?
They are 3 different cats which two of them are of the same type. What makes them different?  their states , behaviours and identity.
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8. Example 4:
Different types of cats
Share the same behaviours
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9. Example 5: How about these cars?
Try to identify their common attributes and behaviours .
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10. Lesson Learned… What can you tell from example 3 to 5?
A group of animals or things that are similar in some way.
They share the same attributes and behaviours.
This group of objects represents a class.
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11. Class ? Object ? Class Object a kind of template.
represents the common structure & behaviour shared by the same type.
A collection of objects of similar type.
must be defined before creating an instance of the class.
a thing, both tangible and intangible.
is comprised of data & operations that manipulate these data.
is called an instance of a class.
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12. Example 6: Variables Represents the data/ attributes variables.
Student
name id
setName()
setId()
Represents the data/ attributes variables.
a set of properties
Methods
class
Represents the behaviours.
A sequence of instructions that a class or an object follows to perform a task.
: Student
name=“Sarah”
id=“1234”
object / instance of the class
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13. Messages An object can’t exist on its own.
An object communicates with other objects.
Therefore, a message is used to instruct a class or an object to perform a task.
An object or a class only responds to messages that it can understand. Messages must match the method that it possess.
A list of messages is called an interface.
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14. Characteristics of OOP
Abstraction
Encapsulation
Inheritance
Polymorphism
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15. Characteristic of OOP Abstraction Encapsulation
the act of representing essential features without including the background details or explanations.
Use to manage complexity
Abstraction can be managed through the use of hierarchical classifications.
The mechanism that binds together code and the data it manipulates and keeps both safe from the outside interference and misuse.
Access to the code & data inside the wrapper is tightly controlled through a well-defined interface.
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16. Example 7: Variables: name student id address course Methods:
changeAddress(String)
changeCourse(String)
Student
INTERFACE
changeAddress(String)
changeCourse(String)
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17. Characteristics of OOP
Inheritance
The process by which one object acquires the properties of another object.
An object need only to define all those qualities that make it unique within its class. It inherits its general attributes from its parent.
A subclass has at least one attribute/method that differs from its superclass
Other names :base class-derived class, parent class-child class
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18. Example 8: Mobile Phone MobilePhone model manufacturer price …
CameraPhone
model
manufacturer
price
pixel …
MobilePhone
model
manufacturer
price …
PdaPhone
model
manufacturer
price
memoryCap …
subclass
superclass
subclass
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19. Characteristics of OOP
Polymorphism
From the Greek, meaning “many forms”.
A feature that allows one interface to be used for a general class of actions.
“one interface, multiple methods”
Can be applied in the overloaded methods (a few methods that have the same name but with different parameters).
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20. Example 9: Class : Rectangle Variables : length, width, height
Methods : ….
displayShape(char simbol)
displayShape(int a)
This class has 2 methods with the same name but with different type of parameters
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21. Conclusion
Elements of an object are attribute, behaviour and identity.
A class is a collection of objects of similar type.
An object is comprised of data and operations that manipulate these data.
Characteristics of OOP is abstraction, encapsulation, inheritance and polymorphism.
NH2008