OOP Concepts

• OOP Features

Encapsulation

• Includes data and actions in a single component
• Classes contain hidden data and actions accessible via specific methods
• Users can only access specific data and actions using encapsulation

Inheritance

• One object (child/subclass) is a specialized form of another object (parent/superclass)
• Used widely in OOP allowing new classes derived from existing ones
• Derived classes inherit data and actions from existing classes
• A child or subclass inherits data and actions of the parent or superclass
• Both Student and Professor classes inherit data name and age and the action walk(int d) from the Person class, its parent

Polymorphism

• Implies "many”, the ability to have many forms
• int add(int a, int b) takes two integer parameters, a and b, adds them, and returns the integer result
• int add(int a, int b, int c) takes three integers, adds them, and returns the integer result
• float add(float a float b) takes two float numbers, adds them, and returns the float result
• Static polymorphism occurs where the compiler understands method signatures and decides the method for a particular method call depending on the number and types of parameters passed
• Dynamic polymorphism occurs when a subclass overrides actions of the superclass
• Subclasses can alter parent class actions and make them specific to their needs

Additional OOP information

• OOP plays a protective role, preventing access to data and actions from outside a class
• Allows for data and actions to only be accessible in specific predefined ways

Advantages of Encapsulation

• Data in a class can be made read or write only
• Classes can restrict data and actions from being altered or called
• Hiding of data storage methods is more convenient than other methods
• Easier maintenance by making changes to data and actions without being apparent on the outside
• Increased usability
• Creation of a "black box" for an object, separating behaviour and implementation by restricting necessary access to data and actions
• Only object behaviour is apparent outside, hiding and protecting internal workings

Advantages of Inheritance

• Extensibility includes all child classes inheriting the actions and data of a parent class
• Child classes can add new functionality, expanding on the parent's actions and data, or redefine them
• Reusability is provided by child classes which inherit actions and data
• Upgrade inherited actions or data in parent class, all child classes automatically use the new version
• Reduces maintenance overheads since an action only needs to be changed once for use in all dependent child classes
• Information hiding: The parent class determines what actions and available data for child classes

Polymorphism Advantages

• Action objects can have the same name but different parameter lists and processes
• Subclasses can have unique actions, and be able to override or improve on parent actions
• Subclasses inherit all parent data and actions, without rewriting code, and can alter actions where necessary, allowing for code reusability
• Polymorphism provides a high degree of decoupling by hiding action implementations
• A common interface exists for a family of objects which abstracts and hides the implementation details

Libraries

• Collection of pre-written code classes which can be used while developing a program
• Simplifies project work with standard, tested working code, acting as a "black box"
• Allows for reuse of code given similar essential functionalities among different applications

Disadvantages of OOP

• OOP may increase complexity, development time, and maintenance costs for small projects with few developers and modules
• Requires care to avoid overly abstract projects, which can be large and complex

Working as a Single Developer

• One person is in charge of the entire development cycle with accountability in design, implementation, testing, and maintenance
• Reasonable for small-scale projects
• Allows for an overall view of the project, with ability to make changes quickly without needing outside communication
• Easier decision making compared to larger teams
• Does not require a common sharing "language" with peers, and no coordination or collaboration problems

Advantages of Programming Teams

• Ability to take on larger projects with more Developers
• Team members bring various ideas without member collaboration
• Strengthens team members and offsets weaknesses
• Team members can concentrate their time and energy without knowing the whole project

Disadvantages of Programming Teams

• Requires honest, well-mannered team communication, and a common "language" for collaboration
• Weak team members may undermine the group
• Decision and project planning takes longer due to a lack of project awareness per member and work on different aspects

Test your understanding of object-oriented programming (OOP) principles. Questions cover encapsulation, inheritance, polymorphism, and advantages/disadvantages of OOP.