Object-Oriented Programming in Java

Object-Oriented Programming (OOP) in Java

Key Concepts

• Classes and Objects:
  • A class is a blueprint or template that defines the properties and behavior of an object.
  • An object is an instance of a class, and has its own set of attributes (data) and methods (functions).
• Inheritance:
  • Inheritance is a mechanism where a new class (sub-class) can inherit the properties and behavior of an existing class (super-class).
  • The sub-class inherits all the fields and methods of the super-class and can also add new fields and methods or override the ones inherited from the super-class.
• Polymorphism:
  • Polymorphism is the ability of an object to take on multiple forms.
  • This can be achieved through method overriding or method overloading.
  • Method overriding is when a sub-class provides a different implementation of a method already defined in its super-class.
  • Method overloading is when multiple methods with the same name can be defined with different parameter lists.
• Abstraction:
  • Abstraction is the concept of showing only the necessary information to the outside world while hiding the internal details.
  • In Java, abstraction is achieved through abstract classes and interfaces.
• Encapsulation:
  • Encapsulation is the concept of bundling data and methods that operate on that data within a single unit (class).
  • In Java, encapsulation is achieved through access modifiers (public, private, protected) and getters/setters.

OOP Principles in Java

• Single Responsibility Principle (SRP):
  • A class should have only one reason to change.
  • A class should have only one responsibility or single purpose.
• Open-Closed Principle:
  • A class should be open for extension but closed for modification.
  • A class should be able to add new functionality without modifying its existing code.
• Liskov Substitution Principle:
  • A sub-class should be able to substitute its super-class.
  • A sub-class should be able to be used in place of its super-class without affecting the correctness of the program.

OOP Benefits in Java

• Code Reusability:
  • OOP allows for code reuse through inheritance and polymorphism.
  • Code reuse reduces the amount of code that needs to be written and maintained.
• Modularity:
  • OOP promotes modularity by breaking down a large program into smaller, independent modules (classes).
  • Modularity makes it easier to develop, test, and maintain a program.
• Easier Maintenance:
  • OOP makes it easier to maintain a program by allowing for changes to be made at a single point without affecting the entire program.
  • OOP promotes loose coupling between classes, making it easier to modify one class without affecting others.

Object-Oriented Programming (OOP) in Java

Key Concepts

• Classes and Objects:
  • Classes define properties and behavior of objects
  • Objects are instances of classes with own attributes and methods
• Inheritance:
  • Mechanism where sub-class inherits properties and behavior of super-class
  • Sub-class can add new fields and methods or override inherited ones
• Polymorphism:
  • Ability of object to take on multiple forms through method overriding or overloading
  • Overriding: sub-class provides different implementation of method already defined in super-class
  • Overloading: multiple methods with same name defined with different parameter lists
• Abstraction:
  • Concept of showing only necessary information to outside world while hiding internal details
  • Achieved through abstract classes and interfaces in Java
• Encapsulation:
  • Concept of bundling data and methods that operate on that data within a single unit (class)
  • Achieved through access modifiers (public, private, protected) and getters/setters in Java

OOP Principles in Java

• Single Responsibility Principle (SRP):
  • Class should have only one reason to change
  • Class should have only one responsibility or single purpose
• Open-Closed Principle:
  • Class should be open for extension but closed for modification
  • Class should be able to add new functionality without modifying existing code
• Liskov Substitution Principle:
  • Sub-class should be able to substitute its super-class
  • Sub-class should be able to be used in place of its super-class without affecting program correctness

OOP Benefits in Java

• Code Reusability:
  • OOP allows for code reuse through inheritance and polymorphism
  • Code reuse reduces amount of code to be written and maintained
• Modularity:
  • OOP promotes modularity by breaking down large program into smaller, independent modules (classes)
  • Modularity makes it easier to develop, test, and maintain a program
• Easier Maintenance:
  • OOP makes it easier to maintain a program by allowing for changes at a single point
  • OOP promotes loose coupling between classes, making it easier to modify one class without affecting others