Object-Oriented Programming Concepts

Chapter 1: Basic Principles: Which Object for Computer Science?

• Software works with data. Effective data use requires understanding, analysis, updating, and storage.
• Object-Oriented Programming (OOP) helps manage data in a clear, logical, and easily followed manner.
• OOP organizes data and associated actions into objects.
• Data classes and objects aid in working with data logically.

Introduction (2)

• Perception of the environment involves noticing specific objects (cars, people, trees, buildings)
• Cognitive mechanisms highlight selective perception (subconscious emphasis on certain aspects)
• An object-oriented approach depends on selective attention to relevant data.
• Ambient and non-salient information (e.g., air, temperature, light) isn't typically part of an object-oriented program
• Distinct structures, shapes, dimensions, and colors ('attributes') are noticeable qualities.
• Perception segmentation results are distinct parts or objects distinguished due to their individual attributes.

The trio <entity, attribute, value>

• The world is represented using entities, attributes, and values.
• An entity is an identifiable or recognizable thing (physical or abstract).
• Examples of entities are cars, people, trees, companies, projects, or events.
• Attributes define and make entities identifiable (e.g., color, age, size for cars)
• Multiple attributes work together to shape a complete entity or idea.

An example of the trio <entity, attribute, value>

• Visual example illustrating the interconnectedness of Student, StudentID, Name, Age, Address, and Mobile number as an example.

What is Object Oriented Programming?

• OOP is a programming paradigm organized around data ("objects") rather than functions/procedures.
• OOP simplifies software development by enabling data modeling.
• OOP uses classes as blueprints for creating objects.
• Using OOP, the programmer can model situations like the real world intuitively.
• OOP leads to less complex programs, faster development times, and easier maintenance.

What is an Object?

• State: data within an object (variables such as color, brand, speed for a car)
• Methods: actions the object can perform (such as accelerate, brake, or honk for a car)
• Identity: what makes an object unique (even if attributes are the same, objects are distinct)

Storage of Objects in Memory

• Object Allocation: Each object gets memory space during creation.
• Primitive Data Types: Programming uses predefined data types (integers, floats, characters) with fixed sizes for memory efficiency.
• Object Attributes: Attributes are represented using primitive types for memory optimization.
• Memory Management: The system allocates required memory space analyzing the object structure for optimal usage.

Example of object memory size calculation

• Numerical Example to Calculate Memory Needed for an Object with specific attributes.

The Referent of an Object

• Unique Object Naming: Objects have unique names for identification.
• Correspondance of Object Name and Memory Address: Names correspond exclusively to memory addresses.
• Memory Address Uniqueness: Each object has a unique memory address.
• Referent as a Variable: The object's name (as a special variable) stores its memory address.
• Referent Storage: Referents are stored in memory dedicated for symbolic names.
• 32-bit Addressing: Memory addresses use 32-bit representation (allowing a large number of identifiable addresses).

The Referent of an Object (2)

• Stack Memory: a short-term data storage area for methods in Java
• Heap Memory: stores objects in Java (managed by Java)
• Objects clean up automatically.

Stack memory example

• Code Example showing how local variables are stored in the stack memory

Heap memory example

• Illustration demonstrating how a new object is allocated in heap memory.

Indirect Addressing

• Multiple Referents for One Object: Multiple names can refer to one object.
• Different Names, Same Object: Objects can have multiple names.
• Independent Contexts: Objects can be referenced without awareness of other contexts within a program.
• Indirect Addressing supports multiple references to the same object without duplication.
• OOP promotes flexible design with different parts of a program using the same object.
• Memory usage efficiency is increased.

Multiple Referents Example

• Code Example illustrating how multiple object references can point to the same object in memory.
• Modifying one reference affects all others.

The Object in Its Passive Version

• Perception of Objects: Objects are seen as wholes (e.g. a car).
• Components of Objects: Objects are comprised of parts.
• Object-Oriented Distinction: The parts of objects are distinguished.
• Public Interface: Interface to access the object.
• Internal Functioning: The object's internal details and component operations, including its internal components.
• Physical Separation: Distinguishing external behavior from internal operation.

Object Composition

• Composition Relationship: Objects are grouped to form a more complex object.
• Dependency: Dependence on the existence of composite objects.
• Access: Accessing components relies on composite objects.
• Real-World Example: A house consists of rooms (as components) which aren't possible independently.

Dependence Relationship

• Dependence Relationship: The existence of one object doesn't rely on another, they interact through references.
• Example: Passengers don't need a car to exist.
• Types of Interactions: Objects interact through references/associations.
• Modeling Flexibility: Flexibility when building models.

The object in its active version

• Dynamic Nature: Objects can change.
• Interaction and Reactions: Objects respond when receiving instructions.
• State Changes: Objects change from one state to another based on interactions.
• Importance of Active Objects: Increased complexity and authenticity through actions.

Object State

• Object state refers to the object's condition based on its attributes.
• State Changes: State alteration due to attribute modification.
• Identity Preservation: Objects retain identity despite state changes.
• Attribute Modification: Changing attribute value without address alteration.
• Frequent Operations: Operations on attributes.
• Lifecycle: Object existence from creation to deletion.

Object Lifecycle

• Object Lifecycle: Object's life cycle from creation to deletion.
• State Transitions: Includes creation, usage, modification, and destruction.
• Object Creation: Allocates memory and initializes attributes.
• Object Usage and Modification: Object's state varies based on interactions.
• Object Destruction: Release of object's memory upon no longer needed.
• Dynamic Representation: State change enables adapting to different phases.

Responsibility

• Object state changes are driven by operations or methods defined for that object.

Exercise

• Example showing how the composition principle affects memory management.

QCM (Multiple Choice Questions)

• Series of multiple-choice questions testing comprehension of different OOP concepts.

Introduction to the concept of a Class

• Classes are blueprints for creating objects.
• Instance variables hold object data. Classes hold the actions (methods) that the object can perform.
• Instance variables are defined outside of methods and belong to the class.

Introduction to the concept of a Class (2)

• Code example of a Vehicle class.
• Demonstrating the structure of a class.

Class Constructor

• Constructors initialize object attributes upon object creation.
• Has the same name as the class.
• Example given in Java code.

Getter

• Method to retrieve an object's attribute value.

Setter

• Method to set or update an object's attribute value.

Object instance

• Objects are instance realizations of classes.
• Objects are created using the "new" keyword.

Example of Object instance

• Code example that shows how to instantiate and use objects.

Instance variables and class variables

• Instance variables are associated with a specific instance of a class.
• Each object (instance) has its own copy of instance variables.
• Instance variables are initialized when an object is created. They can take on differing values.
• Class variables are shared among all instances of a class. Access them directly through the class name, with initialization when the class loads.

Instance variables and class variables (3)

• Static variables are class variables.
• They belong to the class rather than an instance.
• One copy is shared among all class instances.
• Accessed directly by the class's name without instantiating an object.

Instance variables and class variables (4)

• Example code snippet showing declaration of class and instance variables.

QCM

• Questions on the purpose of constructors, this keyword, and functionalities of getter/setter methods, scope of static keyword.

QCM (2)

Questions exploring getter, setter method purposes, scope of static keyword.

QCM (3)

• Questions probing the distinctions between instance and class variables.

Object-Oriented Programming (OOP) Languages vs. Languages Manipulating Objects

• OOP languages allow programmers to create their own classes.
• OOP languages modify and work with the classes.
• Predefined classes are provided in other languages (e.g., JavaScript for web pages).

Executing the Method on a Specific Object

• turnOn() method applies to a specific object.
• The dot (.) connects the method to the object.
• The method accesses attributes of the specific object.
• Example code demonstrates using the method on a specific object.

How Objects Communicate

• Objects interact by sending messages to each other through methods.

Finding Message Recipients

• Identifying the object type.
• Storing the object reference within the other object.

Example: Finding Message Recipients (2)

• Illustrative examples of a Car and Parking class.

What is Inheritance?

• Inheritance is a fundamental OOP concept.
• Uses a hierarchy to organize classes (subclass/child class derives from superclass/parent class)

Hierarchy of Objects

• Object categories are organized hierarchically (general to specific).
• Example relationship between "phone" and "iPhone 14".

Contextual Dependence on the Right Taxonomic Level

• Using broad terms (e.g., "car") is fine in everyday conversation.
• But specific vehicles descriptions are needed in a technical context.
• Describing a technical issue with a car without specifying its make and model won't be enough information.

Contextual Dependence on the Right Taxonomic Level (2)

• Context matters when deciding the level of detail.
• Example with a car's malfunction.

Polymorphism

• Different objects respond to the same message or method in object-oriented programming in different ways.
• Using methods/reference variables with different behaviors in various programming contexts.

Polymorphism example

• Click on a computer screen invokes various actions on individual objects/windows on the screen.

References

• List of resources used.

Test your understanding of key concepts in object-oriented programming (OOP) with this quiz. Explore topics like composition relationships, lifecycles of objects, and the roles of methods and attributes. This quiz is ideal for beginners looking to solidify their grasp on Java's OOP principles.