A class is a blueprint or template for creating objects. It defines the properties (attributes) and behaviors (methods) that objects of the class will have.
An object is an instance of a class. It represents a real-world entity and encapsulates data and methods related to that entity.
Encapsulation is the concept of bundling the data (attributes) and the methods (functions) that operate on the data into a single unit, known as a class.
Access modifiers like private, public, and protected are used to control the visibility of class members, allowing data hiding and implementation abstraction.
Inheritance is a mechanism by which a new class, called a subclass or derived class, can inherit properties and behaviors from an existing class, known as a superclass or base class.
It promotes code reuse and allows the creation of a hierarchy of classes.
Polymorphism allows objects of different types to be treated as objects of a common type. It is achieved through method overloading and method overriding.
Method Overloading: Having multiple methods in the same class with the same name but different parameter lists.
Method Overriding: Providing a specific implementation for a method in a subclass that is already defined in its superclass.
Abstraction is the process of hiding the implementation details and showing only the essential features of an object.
Abstract classes and interfaces are used to achieve abstraction in Java. Abstract classes can have abstract methods, and interfaces can declare abstract methods that must be implemented by concrete classes.
Association: Represents a relationship between two or more classes. It can be one-to-one, one-to-many, or many-to-many.
Aggregation: Represents a "whole-part" relationship where a whole object contains parts that can exist independently.
Composition: Represents a stronger form of aggregation where the parts are so closely tied to the whole that they cannot exist independently.