Java Object-Oriented Programming

Study Notes

Class: A blueprint or template that defines the properties and behaviors of an object.
Object: An instance of a class, which has its own set of attributes (data) and methods (functions).
Inheritance: A mechanism that allows one class to inherit the properties and behaviors of another class.
Polymorphism: The ability of an object to take on multiple forms, depending on the context in which it is used.
Abstraction: The concept of showing only the necessary information to the outside world while hiding the internal details.
Encapsulation: The concept of bundling data and methods that operate on that data within a single unit (class).

A class is defined using the class keyword.
A class can have multiple constructors, which are used to initialize objects.
An object is created using the new keyword, followed by the constructor.
Classes can have instance variables (data members) and instance methods (functions).

A child class inherits the properties and behaviors of a parent class using the extends keyword.
A child class can override the methods of a parent class.
A child class can also add new methods or variables.

Method overriding: When a child class provides a different implementation of a method that is already defined in its parent class.
Method overloading: When multiple methods with the same name can be defined with different parameter lists.
Runtime polymorphism: When the actual method to be called is determined at runtime, rather than at compile time.

Abstract classes: Classes that cannot be instantiated and are used as a base class for other classes.
Abstract methods: Methods that are declared but not implemented in an abstract class.
Interfaces: Abstract classes that define a contract that must be implemented by any class that implements it.
Access modifiers: Public, private, protected, and default access modifiers are used to control access to classes, variables, and methods.

Code reuse: Through inheritance and polymorphism, code can be reused in multiple contexts.
Modularity: Code is organized into modular units (classes) that can be easily maintained and updated.
Easier maintenance: Changes to the code can be made at a single location, without affecting other parts of the program.

Class: A blueprint or template that defines properties and behaviors of an object.
Object: An instance of a class, with its own set of attributes (data) and methods (functions).
Inheritance: A mechanism that allows one class to inherit properties and behaviors of another class.
Polymorphism: Ability of an object to take on multiple forms, depending on the context.
Abstraction: Concept of showing only necessary information to the outside world while hiding internal details.
Encapsulation: Bundling data and methods that operate on that data within a single unit (class).

A class is defined using the class keyword.
A class can have multiple constructors, used to initialize objects.
An object is created using the new keyword, followed by the constructor.
Classes can have instance variables (data members) and instance methods (functions).

A child class inherits properties and behaviors of a parent class using the extends keyword.
A child class can override methods of a parent class.
A child class can also add new methods or variables.

Method overriding: A child class provides a different implementation of a method already defined in its parent class.
Method overloading: Multiple methods with the same name can be defined with different parameter lists.
Runtime polymorphism: Actual method to be called is determined at runtime, rather than at compile time.

Abstract classes: Classes that cannot be instantiated and are used as a base class for other classes.
Abstract methods: Methods that are declared but not implemented in an abstract class.
Interfaces: Abstract classes that define a contract that must be implemented by any class that implements it.
Access modifiers: Public, private, protected, and default access modifiers control access to classes, variables, and methods.

Code reuse: Through inheritance and polymorphism, code can be reused in multiple contexts.
Modularity: Code is organized into modular units (classes) that can be easily maintained and updated.
Easier maintenance: Changes to the code can be made at a single location, without affecting other parts of the program.

Java has two main categories of data types: primitive and reference
Primitive Data Types:
- Integers: byte (e.g., 1), short (e.g., 10), int (e.g., 100), long (e.g., 1000)
- Floating-point numbers: float (e.g., 1.0), double (e.g., 2.0)
- Characters: char (e.g., 'A')
- Boolean: boolean (e.g., true/false)
Reference Data Types:
- Arrays (e.g., int[] myArray = {1, 2, 3})
- Classes and Objects (e.g., Person person = new Person("John", 25))

Arithmetic Operators:
- Addition: a + b
- Subtraction: a - b
- Multiplication: a * b
- Division: a / b
- Modulus: a % b
Comparison Operators:
- Equal: a == b
- Not Equal: a != b
- Greater Than: a > b
- Less Than: a < b